Oxygen Scavengers for Plastic Packaging: 5 Types, Mechanisms, Dosage and Selection

An oxygen scavenger is an additive or system that chemically consumes the oxygen left inside a package and the oxygen that permeates through its wall, which is what separates it from a passive barrier such as EVOH or MXD6 that only slows permeation down. Five chemistries do this work, from reduced iron powder that needs moisture before it starts to an oxidisable polymer that a few hundred parts per million of cobalt turn into an oxygen sink, so which one belongs in which package, and what does European law allow? One gram of reduced iron consumes about 300 cm³ of oxygen, and the cobalt-catalysed systems used in PET bottles run on 10 to 300 ppm of cobalt metal.

The 5 chemistries, in the order used throughout this page, are iron-based systems built on reduced iron powder, oxidisable polymers such as nylon-MXD6 activated by a cobalt carboxylate, ascorbate and sulfite systems, palladium-catalysed hydrogen systems in the closure, and enzymatic systems based on glucose oxidase. Where the chemistry sits matters as much as what it is, because the same reaction is dosed and regulated differently in a sachet, a closure liner, a bottle wall and a film layer, which is the second axis of this family.

This reference separates the active scavenger from the passive barrier, explains the iron and cobalt mechanisms, sets out the 5 types with their patent evidence and the packages that use them, publishes every dosage level in the public record with the basis of each number, gives 7 selection steps and the haze and colour cost in recycled PET, describes how performance is measured, sets out the EU and US regulatory position and the EPBP, APR and PPWR recyclability conditions, names the suppliers, and closes with the 3 substance pages in the plastic additives database.

The table below compares the 5 technologies on chemistry, trigger, position in the package, clarity and whether each exists as a compounded plastic additive at all.

Sachets and labels are listed for context. They are packaging inserts, not additives compounded into a polymer, and this reference covers them only as the alternative to an in-wall system.

What Is an Oxygen Scavenger in Plastic Packaging?#

An oxygen scavenger is an additive or system that chemically consumes oxygen inside a plastic package, both the oxygen trapped in the headspace at filling and the oxygen that permeates through the package wall during storage. The same function carries four names in the trade and one in law: oxygen absorber, O2 scavenger, active oxygen barrier and the abbreviation OS, and, in the European Union, part of an active material. Regulation (EC) No 450/2009 defines active materials and articles as those intended to extend the shelf-life or to maintain or improve the condition of packaged food, which describes a scavenger precisely.

If a package already carries a barrier layer, why add something that consumes oxygen at all? A barrier slows ingress and removes nothing that is already inside, and its permeation rate is never zero, so a filled bottle keeps gaining oxygen for as long as it stands on the shelf. Oxygen scavengers are one of the functional families among the 43 types of plastic additives covered on this site, and one of the few designed to make an oxidation reaction happen rather than to suppress one.

Active oxygen barrier or passive barrier? The distinction that decides the material#

A passive barrier such as EVOH, MXD6 or a silicon oxide coating slows oxygen down, while an active scavenger consumes it: an oriented MXD6 film transmits about 2.8 cc of oxygen per square metre per day at 23 °C and 60 % relative humidity, whereas a cobalt-catalysed wall in the Oxbar patent is claimed down to 0.1 cm³ per square metre per atmosphere per day. There are 2 ways to keep oxygen away from a packed food, and they are not interchangeable: the passive route controls the rate at which oxygen arrives, the active route controls how much oxygen is present, and barrier additives and scavengers are sold by the same houses under one catalogue heading.

MXD6 belongs in both columns below, because on its own it is a passive barrier polymer and, once a cobalt carboxylate is present in the same wall, it becomes the oxidisable substrate of an active system. That double role is why a bottle specification has to say whether the nylon phase is there to slow oxygen or to consume it.

MXD6 belongs in both columns: alone it is a passive barrier, and with a cobalt catalyst it becomes the oxidisable substrate of an active system.

The permeability values here are Mitsubishi Gas Chemical's data for its MX-Nylon grades, at 23 °C on 20 µm film, in cc/(m²·day·atm): oriented MXD6 2.8, 3.5 and 5.5 at 60, 80 and 90 % relative humidity, non-oriented MXD6 4.3, 7.5 and 20, oriented PET 80, oriented nylon 6 between 40 and 90, and EVOH-32 between 0.5 and 50 depending on humidity. In whole bottles the same data set reports 0.027 cc per bottle per day at 0.21 atm for plain PET, 0.016 for a 5 % MXD6 blend, 0.011 for a 10 % blend and 0.0075 for a three-layer bottle with 10 % MXD6, so the best passive construction still leaves a quarter of the ingress, and the passive routes are compared on barrier additives for plastic packaging.

Oxygen scavenger or desiccant: what each one removes#

An oxygen scavenger removes oxygen and a desiccant removes water, and the two are not interchangeable: calcium oxide in a desiccant concentrate binds water irreversibly as calcium hydroxide, while an iron scavenger needs at least about 65 % relative humidity before it starts to oxidise at all. Sängerlaub and colleagues set that distinction out in Materials in 2019: chemisorption on calcium oxide is irreversible, unlike the physisorption of silica gel or a zeolite, which releases the water again. The dosing logic differs too, since one supplier rule for a moisture-binding concentrate is 1 % of masterbatch per 0.15 % of moisture in the resin. The two mechanisms also conflict: a moisture-activated iron system and a drying additive work against each other in the same package, so a dry product loses either the iron chemistry or the desiccant, and moisture control in the melt belongs instead to a desiccant masterbatch.

Sachet, closure or bottle wall: the 3 places a scavenger can sit#

The same scavenging chemistry behaves very differently depending on where it sits, and there are 4 positions: a sachet or label inside the package, a liner or compound in the closure, a layer or blend in the package wall, and a scavenging layer in a film structure. The 4 positions and what each implies are listed below.

• Sachet or label. A permeable pouch or adhesive label holding iron powder, ascorbate or sulfite, which is a packaging insert rather than a compounded additive.
• Closure liner or closure compound. A scavenging liner or a whole closure compounded with the active, which keeps the chemistry out of the container wall and out of the PET recycling stream.
• Wall of the container. A monolayer blend of an oxidisable polymer and a catalyst, or a scavenging middle layer, which is the construction that carries the PET bottle business.
• Film layer. A dedicated scavenging layer inside a coextruded flexible structure, usually iron-loaded, behind a sealant layer.

The position decides the regulatory and recyclability question as much as the chemistry does: the same iron powder is a packaging insert in a sachet and a plastic component under the migration limits of Regulation (EU) No 10/2011 once it enters a film.

How Do Oxygen Scavengers Work?#

Every commercial oxygen scavenger works by oxidising something on purpose: either a sacrificial substance such as iron powder or ascorbate, or, in the systems used in bottle walls, an oxidisable polymer whose reaction with oxygen a transition-metal catalyst speeds up. A third route oxidises no solid at all and burns hydrogen instead, combining hydrogen released inside a closure with oxygen over a catalyst to give water. All three end with an oxygen molecule removed from the package, and they differ in what is consumed, what is left behind and what must be present first.

How iron scavenges oxygen: moisture-activated oxidation#

An iron scavenger works in 3 steps: moisture in the package reaches the iron powder, the sodium chloride activator puts the iron into solution at the particle surface, and the iron oxidises, taking oxygen out of the atmosphere around it. The 3 steps are set out below.

1. Wet the particle surface. Water vapour from the packed food reaches the reduced iron powder, and the reaction needs at least about 65 % relative humidity to begin.
2. Dissolve the activator. Sodium chloride brings iron into solution at the particle surface and catalyses the next step.
3. Oxidise the iron. Dissolved iron reacts with oxygen to form iron oxide, removing oxygen from the headspace and from the ingress through the wall.

Prerna Gupta at Lovely Professional University set out the working figures in a 2023 review of oxygen absorbers in the Journal of Food Science and Technology. One gram of iron consumes about 300 cm³ of oxygen at standard temperature and pressure, particles are typically 10 to 30 µm, and the reaction can take headspace oxygen below 0.01 %. Rate is a separate question from capacity, and the one measured value in that review comes from Gibis and Rieblinger in 2011: a polyethylene film containing iron powder took up 33 cm³ of oxygen per square metre in 4 days. The moisture requirement decides most applications, because a product with no water activity never activates the iron.

How cobalt catalyses the oxidation of a polymer#

In a cobalt-catalysed system the polymer itself is the fuel: a cobalt carboxylate speeds up the reaction between oxygen and an oxidisable segment in the wall, so the wall consumes oxygen instead of merely resisting it. The CMB Foodcan patent behind the Oxbar system, US 5,021,515, filed by Cochran, Folland, Nicholas and Robinson with a priority date of 27 July 1987, describes the principle as metal-catalyzed oxidation of an oxidizable organic component in the wall, and claims cobalt at at least 10 ppm, preferably 50, more preferably 100, kept below 300 and more preferably below 250 ppm, with 200 ppm in the worked example.

The proof that cobalt acts as a catalyst rather than a reagent is in that example: a 0.3 mm wall reached no measurable permeation within 3 days and scavenged at least 0.9 mmol of oxygen while only 0.11 mmol of cobalt was present, roughly eight oxygen molecules for every cobalt atom. The reaction exploited is autoxidation, the same radical chain described under polymer degradation and normally suppressed by an antioxidant package, promoted here in one phase of the blend. A scavenging blend is therefore a formulation problem rather than a drop-in, because the stabiliser system has to protect the PET while leaving the oxidisable phase free to react.

The table below sets out what each type oxidises, what starts the reaction, what it leaves behind and whether the active is consumed.

No primary source on file gives reaction rates or capacities for the ascorbate, sulfite or enzymatic systems in a compounded plastic.

Induction period, capacity and how long a scavenger keeps working#

A scavenger keeps working until its capacity is used up, which is a finite quantity: about 300 cm³ of oxygen per gram of iron in an iron system, and in a cobalt-catalysed wall the amount of oxidisable polymer that is present. Two properties decide whether that capacity is useful. The first is the induction period, the delay before the system takes up oxygen at full rate, which matters because a bottle blown today may be filled three weeks later. The second is rate, since capacity released too slowly never protects a short shelf life and capacity released too quickly is spent before shipping. The Oxbar example reports no measurable permeation within 3 days, which is a rate statement rather than a service life.

Service life is where the public record thins out. No primary, non-supplier source in our source library gives a service life for any scavenging system in a finished package, so every duration on this page belongs to the bulletin that published it. Avient describes its low-haze Amosorb 4020G grade as having no induction period and as giving 40 % increased shelf-life at maximum allowable use limit, and describes the ColorMatrix Capture closure system as extending shelf life by up to 24 months. Those are supplier claims about named grades in named packages, not rules of thumb.

5 Types of Oxygen Scavengers for Plastics#

The 5 types of oxygen scavenger used in and around plastic packaging are iron-based systems, oxidisable polymers with a cobalt catalyst, ascorbate and sulfite systems, palladium-catalysed hydrogen systems built into the closure, and enzymatic systems. Two of the five, the ascorbate and sulfite group and the enzymatic group, are barely present as compounded plastic additives, and this page says so rather than describing them as if grade data existed. The order below is commercial weight combined with the depth of primary evidence, and it runs through every table, image and list here.

1. Iron-based scavengers#

Iron-based scavengers are reduced iron powder with a sodium chloride activator, and they are the oldest and highest-volume oxygen scavenging chemistry: 1 gram of iron consumes about 300 cm³ of oxygen, enough to take a sealed headspace below 0.01 % oxygen. The powder is fine, typically 10 to 30 µm according to Gupta's 2023 review, which gives it the surface area to react at a useful rate. In plastics it reaches three formats: sachets and adhesive labels, closure liners, and a loaded layer inside a coextruded film, where an iron-loaded polyethylene film took up 33 cm³ of oxygen per square metre in 4 days. Iron migration from a plastic component is capped at 48 mg/kg under Annex II of Regulation (EU) No 10/2011.

Three limits decide where iron can be used, and all three follow from what iron is. It needs moisture, since the reaction does not start below roughly 65 % relative humidity, which rules out dry and low-moisture products. It is opaque and iron-coloured, so it cannot go into a clear bottle wall at any useful level. It is metallic and ferromagnetic, which is why an iron-loaded component is kept out of the clear PET bottle stream, where the non-PET fraction matters.

2. Oxidisable polymer plus cobalt catalyst: MXD6, polybutadiene copolyester and PCOE#

The oxygen scavenger used in PET bottles is not one substance but a pair: an oxidisable polymer blended into or layered inside the wall, and a cobalt carboxylate at a few hundred parts per million that makes its reaction with oxygen fast enough to matter. Three oxidisable substrates carry this class commercially. Nylon-MXD6 is the substrate of the Oxbar system, whose patent example blends 96 % PET with 4 % MXD6 and 200 ppm of cobalt for lager beer, white wine and juices. A polybutadiene-segmented copolyester is the substrate of the Amosorb system, US 6,083,585, filed by Cahill and Chen at BP Amoco on 23 September 1996, which claims polybutadiene oligomer segments at 0.5 to 12 wt% of the copolymer, preferably 2 to 8 and especially 2 to 6 wt%, with cobalt at 10 to 300 ppm and especially 50 to 200 ppm. Polycyclooctene with cobalt stearate is the third, the system the EFSA CEP Panel assessed in 2022.

The regulatory position differs for each, and none is simply approved. The Amosorb-type copolymer holds a Union list entry in Regulation (EU) No 10/2011 as FCM 979, only to be used in PET at a maximum level of 5 % w/w. The polycyclooctene system was evaluated by the EFSA CEP Panel in 2022 in the EFSA Journal 20(6):7364, for all foods at or below room temperature for up to 6 months in a multilayer structure, and the Panel was not able to conclude on its safety because of insufficient data on the oxidation products, although cobalt migration was not detected at a limit of detection of 0.0006 mg/kg against an SML of 0.05 mg/kg. MXD6 has no scavenger-specific authorisation: its monomers are listed instead, 1,3-benzenedimethanamine as FCM 421 under group restriction 34 with an SML(T) of 0.05 mg/kg, and adipic acid as FCM 303. Above all three sits the Union list of authorised active and intelligent substances under Regulation (EC) No 450/2009, which had not been adopted as of 22 September 2026.

The Union list of authorised active and intelligent substances under Regulation (EC) No 450/2009 had not been adopted as of 22 September 2026; only a register of substances with a valid application is published.

3. Ascorbate and sulfite systems#

Ascorbate and sulfite systems use a sacrificial salt that oxidises in the presence of moisture, and in packaging they appear mainly in sachets and labels rather than compounded into a polymer. Our source library holds no in-polymer level, no capacity and no food-contact entry for an ascorbate or sulfite scavenger used as a plastic additive, and that absence is stated here rather than filled with numbers from another industry. Sulfite chemistry is the source of most of the confusion around the head term, because sodium sulfite is the dominant oxygen scavenger in boiler feedwater treatment, where it is dosed into water to protect metal.

4. Palladium-catalysed hydrogen systems in the closure#

A palladium-catalysed hydrogen system moves the whole scavenging function out of the bottle and into the cap: hydrogen released inside a two-layer plug-seal closure combines with oxygen over a catalyst and leaves water behind. Avient describes its ColorMatrix Capture system as sitting entirely in a one-piece, two-layer HDPE or PP plug-seal closure, as compatible with hot-fill and aseptic filling, as holding FDA food-contact status, as recognised under the APR Critical Guidance protocol, and as extending shelf life by up to 24 months. Each of those properties is a supplier statement about one commercial system, not an independent finding.

The position, not the chemistry, carries the trade-off. Because nothing is added to the PET wall, the bottle stays a plain PET bottle for recycling and the yellowing an oxidisable phase causes in recycled PET does not arise, while capacity is limited to what the closure holds and the function is tied to one supplier's design. The rest of the closure package is covered on additives for caps and closures.

5. Enzymatic scavengers#

Enzymatic scavengers use an enzyme such as glucose oxidase to consume oxygen through a biochemical reaction rather than a metal oxidation, and in packaging they are still mostly a coating and film technology rather than a compounded additive. No primary source on file gives an enzyme loading, a capacity or a food-contact status for an enzymatic scavenger in a compounded plastic, so the evidence for this type is not established and no level is stated here. The claim that enzymatic systems suit moisture-sensitive products circulates widely, and this page does not repeat it, because an enzyme needs both water and a substrate to work at all.

Which Polymers and Packages Use Oxygen Scavengers?#

Oxygen scavengers are used where the product loses value to oxygen faster than the package can keep it out: beer, wine, fruit juice, sauces and other oxygen-sensitive foods in PET bottles, and meat, fish and ready meals in film and tray structures. The Oxbar patent names lager beer, white wine and juices as its targets, the same list a bottle producer would give today, because those products combine a long distribution chain with a flavour that oxidises measurably. The host polymer follows the package rather than the chemistry: PET in bottles and trays, HDPE or PP in closures, polyethylene and coextruded structures in film. What the technology buys shows in the ingress numbers, since a plain PET bottle admits 0.027 cc of oxygen per day at 0.21 atm against 0.0075 cc for a three-layer wall with 10 % MXD6, and an active system removes what remains. The full food-contact stack for these packages is on additives for food packaging.

PET bottles: oxygen scavengers next to reheat and acetaldehyde scavengers#

A PET preform rarely carries only one functional additive: an oxygen scavenger in the wall usually sits next to a reheat additive that speeds up preform heating and, in water and beverage bottles, an acetaldehyde scavenger that protects taste. Each has its own Union list ceiling, its own effect on colour and its own recycling verdict inside one wall of perhaps 0.3 mm. The scavenger is the largest by mass, at a few per cent of the wall against a few hundred parts per million for the other two, and grade-by-grade selection is covered on oxygen scavengers for PET bottles.

Reheat additives are the smallest additions and the most consequential for colour. Carbon black is FCM 411, titanium nitride nanoparticles FCM 807 for PET only at up to 20 mg/kg, reduced tungsten oxide FCM 1064 with an SML of 0.05 mg tungsten per kg, and iron phosphide FCM 607 for PET only, and each absorbs near-infrared light to shorten the oven time before stretch-blow moulding. These are covered on IR absorbers and reheat additives, including why the particles that save energy can darken recycled flake.

Acetaldehyde scavengers occupy the third slot, because PET generates acetaldehyde during processing and it is detectable by taste in still water. Anthranilamide holds the Union list entry for this job, FCM 164, with an SML of 0.05 mg/kg and a restriction to PET for water and beverages, at 200 to 500 ppm for effective scavengers. The taste-protection additive is covered on acetaldehyde scavengers for PET bottles.

How Much Oxygen Scavenger Does a Package Need?#

There is no single dosage for an oxygen scavenger, because the level is set by how much oxygen the package has to absorb over its shelf life rather than by the polymer it goes into. A level means something only together with a package size, a wall thickness and a storage time, which is what a vendor datasheet leaves out. The published numbers fall into four kinds that must never be mixed: a patent claim range, a regulatory ceiling, a recyclability condition and a supplier level for one grade.

A patent claim range is what the inventor claimed, not a formulation recommendation. A supplier level is what one grade's bulletin states. Neither is a specification for your package.

Levels arrive in three units, since the oxidisable polymer is quoted in weight per cent of the article, the cobalt in parts per million of metal and the concentrate in let-down ratio. The unit rules, including conversion to wt%, ppm and let-down ratio, apply as to any other concentrate.

What the published dosage evidence actually shows#

Two patent families filed nine years apart converge on the same cobalt window: at least 10 parts per million to work at all, 50 to 200 parts per million in practice, and below 300 parts per million in both claim sets. CMB Foodcan claimed at least 10 ppm, preferably 50 and more preferably 100 ppm, below 300 and more preferably below 250 ppm, with 200 ppm in its example. BP Amoco, filing in 1996 on a different substrate for a different company, claimed 10 to 300 ppm with 50 to 200 ppm especially preferred. Two teams, one on nylon and one on a polybutadiene copolyester, reached the same catalytic window, which is stronger evidence for the working level than any datasheet.

The ceilings that constrain a European formulation come from elsewhere. The hard regulatory number is the 5 % w/w maximum on the Amosorb-type copolymer in PET under FCM 979, a food-contact limit rather than a performance limit. The EPBP condition on PA-MXD6, up to 5 wt% in clear and white three-layer bottles and 6 wt% in coloured and opaque ones with no tie layers, is a recyclability limit with no legal force that still decides whether customers accept the bottle. The chemistry imposes no ceiling below those two, since more oxidisable polymer means more capacity, more haze and more non-PET content, so the formulator chooses between shelf life and recyclability rather than searching for an optimum dose.

Masterbatch, liquid concentrate and multilayer: how scavengers are dosed#

Oxygen scavengers reach the machine in 3 forms: a solid oxygen scavenging masterbatch let down at a set ratio, a liquid concentrate metered into the melt, and a separate resin for a multilayer middle layer. The choice is a plant decision, since an oxygen scavenging masterbatch fits an existing preform machine with a gravimetric feeder, a liquid concentrate needs a dosing pump, and a multilayer route needs a co-injection tool. All three deliver the same pair of actives, an oxidisable polymer and a cobalt carboxylate, as an additive masterbatch or its liquid equivalent rather than as neat catalyst.

The 3 supply forms and what each demands of the plant are listed below.

• Solid concentrate. Pellets let down at the preform machine at a stated ratio, typically a few per cent, through the same feeder as a colour concentrate.
• Liquid concentrate. A pumped concentrate metered into the melt stream, which gives fine control of the let-down ratio and avoids a second solid stream.
• Multilayer middle-layer resin. A separate resin injected as an internal layer in a three-layer preform, which keeps the active away from both surfaces and, under the EPBP guideline, must be built without tie layers if the bottle is to stay recyclable.

Any dose can be checked against the target active level with the let-down ratio calculator before a trial is booked.

How Do You Select an Oxygen Scavenger? 7 Steps#

Select an oxygen scavenger in 7 steps: quantify the oxygen load, check whether moisture is available, decide where the scavenger sits, screen the food-contact route, check the recycling guidelines, check the optical cost, then confirm by measuring the filled package. The steps run in that order because each can eliminate a chemistry, and the cheapest elimination comes first.

1. Quantify the oxygen load. Add the headspace volume at filling to the wall ingress over the shelf life. A plain PET bottle admits about 0.027 cc per bottle per day at 0.21 atm and a three-layer wall with 10 % MXD6 about 0.0075 cc, so fix the passive construction first.
2. Check whether moisture is available. An iron system needs at least about 65 % relative humidity, so a dry product points to a cobalt-catalysed wall or a closure.
3. Decide where the scavenger sits. A wall system enters the recycling stream, a closure leaves the wall untouched, and a sachet changes nothing in the formulation.
4. Screen the food-contact route in every market. The Amosorb-type copolymer is capped at 5 % w/w in PET under FCM 979, the EFSA opinion on the polycyclooctene system could not conclude, and the Union list under Regulation (EC) No 450/2009 does not yet exist.
5. Check the recyclability guidelines for the stream the package enters. EPBP conditions and the APR PET-CG-01 protocol after ageing under PET-P-12 decide acceptance, and an untested additive is detrimental.
6. Check the optical cost. Haze, b* shift and behaviour in recycled PET are grade-specific, and belong on trials at the intended recycled content.
7. Confirm by measurement on the filled package. A plaque proves the chemistry works; only the filled, sealed and stored package proves the system protects the product.

The general method behind these steps is on how to select plastic additives.

Other families can be filtered with the additive finder by polymer and function when the oxygen problem turns out to be a barrier or a moisture problem.

How Do Oxygen Scavengers Affect Haze, Colour and Recycled PET?#

An oxidisable polymer in a PET wall is a second polymer in a clear bottle, and a second polymer is a haze source, a yellowing source and a contaminant that every later melt history has to carry. That mechanism holds whatever the grade: two polymers with different refractive indices scatter light at their phase boundaries, and an oxidising phase produces coloured degradation products. Haze is quantified by haze and clarity measurement on the finished wall rather than estimated from the recipe.

Colour behaves the same way and survives recycling. Suppliers report the shift as b* or as a yellowness index, and North American bulletins call it color. Avient states that its Amosorb 4020G low-haze grade gives up to 50 % lower haze than previous grades and halves the b* shift, which is only meaningful as an admission that scavenging grades raise haze and yellow the wall. The same source reports a recycling study on the nylon-based SolO2-2 grade at 4 % with 0.09 % amber, in which L* moved from 36.3 to 40.4 over 5 melt histories, and states that one booster grade performs consistently at 25, 50 and 100 % recycled PET content. The wider colour question is covered on additives for recycled plastics.

The closure route exists to avoid this trade-off. Because a palladium-catalysed hydrogen system sits in the cap and nothing enters the PET wall, the bottle carries no second polymer, no added haze and no yellowing into the recyclate, at the cost of a capacity limited by the closure volume.

How Is Oxygen Scavenging Performance Measured?#

Oxygen scavenging performance is measured in 3 ways: as the oxygen that passes a film of stated thickness, as the oxygen that enters a whole bottle per day, and as the oxygen left in the headspace of a filled and sealed package. No value means anything without its conditions, since oxygen transport changes with temperature, humidity and thickness, and nylon and EVOH change with humidity by more than an order of magnitude. Our source library holds no standard number for oxygen transmission rate testing here, so the 4 measurements below are named by what they measure and by their units.

• Film permeability, in cc/(m²·day·atm), with temperature, thickness and relative humidity: Mitsubishi Gas Chemical reports 2.8 for oriented MXD6 at 23 °C, 20 µm and 60 % RH, rising to 5.5 at 90 % RH.
• Wall permeance, in cm³/(m²·atm·day), the unit of the Oxbar claim of not more than 10.0 and most especially not more than 0.1.
• Bottle ingress, in cc per bottle per day at 0.21 atm, the only unit that reflects the real geometry: 0.027 for plain PET, 0.0075 for a three-layer wall with 10 % MXD6.
• Headspace oxygen in the filled and sealed package, the endpoint that matters commercially, which an iron system can take below 0.01 %.

A fifth test is not a performance measurement but decides market access: the APR route evaluates a scavenger by PET-CG-01 after ageing under PET-P-12, so a package that passes every oxygen measurement can still fail the stream it was designed for. All methods are indexed under testing plastic additives.

How Are Oxygen Scavengers Regulated?#

An oxygen scavenger in food packaging sits under 2 European regimes at once: Regulation (EC) No 450/2009 for active and intelligent materials, and Regulation (EU) No 10/2011 for every plastic component it is made of. A third layer applies to the metal, since cobalt and iron each carry a migration limit in Annex II, and a fourth arrives through the recycled-content obligations of Regulation (EU) 2025/40. The general limits of Regulation (EU) No 10/2011 apply throughout: a generic specific migration limit of 60 mg/kg, an overall migration limit of 10 mg/dm² or 60 mg/kg for infant food, and 0.01 mg/kg behind a functional barrier. Every instrument named here is summarised in plastic additive regulations.

EU: active materials under Regulation (EC) 450/2009 and the plastics rules of 10/2011#

Regulation (EC) No 450/2009 defines an active material as one intended to extend the shelf-life or to maintain or improve the condition of packaged food, which is exactly what an oxygen scavenger does, but its Union list of authorised active substances had not been adopted as of 22 September 2026. Only a register of substances with a valid application is published, which means no oxygen-scavenging active substance holds an authorisation under that regulation, and it equally means none is banned by it. The active and intelligent packaging rules that govern labelling, the requirement that the release of substances be intentional and the ban on misleading the consumer about the condition of the food apply in full in the meantime.

Compliance therefore runs through the plastics regulation. An active material must also comply with Regulation (EU) No 10/2011 for every plastic component it contains, which is why the substances below matter individually: the copolymer, the monomers, the catalyst metal and the acid of the catalyst salt each carry an entry or an Annex II limit. Where a passive layer separates the active layer from the food, that layer can act as a functional barrier, and the 0.01 mg/kg limit for non-authorised substances behind such a barrier applies.

Values verified against the consolidated text of Regulation (EU) No 10/2011 of 16 March 2025. No oxygen-scavenging system holds an authorisation under Regulation (EC) No 450/2009, because that Union list has not been adopted.

How the Union list works, including the difference between an authorised substance and a substance behind a functional barrier, is explained on EU 10/2011.

Cobalt: the migration limit and the REACH status of the catalysts#

Cobalt is the reason this family carries a regulatory question mark: its specific migration limit in European food-contact plastics is 0.05 mg/kg, and five cobalt salts sit on the REACH Candidate List as carcinogens. The measured evidence is reassuring so far. In the EFSA CEP Panel's 2022 assessment of the polycyclooctene system with cobalt stearate, cobalt migration was not detected at a limit of detection of 0.0006 mg/kg, two orders of magnitude below the limit, and cobalt salts are permitted through the Article 6(3)(a) salt rule where the corresponding acid is authorised. Cobalt neodecanoate carries the further restriction of FCM 819, which excludes it from contact with fatty foods.

The distinction that matters under REACH is between the cobalt salts on the Candidate List and the carboxylates used as catalysts. The five listed as carcinogens under Article 57(a) are cobalt(II) diacetate, cobalt carbonate, cobalt sulphate, cobalt dinitrate and cobalt dichloride, all simple inorganic or short-chain salts. Cobalt neodecanoate (CAS 27253-31-2, EC 248-373-0) and cobalt stearate (CAS 13586-84-0, EC 237-016-4) were not on the Candidate List in the compilation checked for our source library, and every listed plastic additive is tracked on the SVHC Candidate List. The hazard picture from notified classifications is separate: the registrant classification for cobalt stearate is Skin Sens. 1 H317, STOT RE 1 H372 and Aquatic Chronic 3 H412, other notifiers also report H315, H319, H334, H351 and H411, and no harmonised entry was verified in our sources.

US: FDA food-contact routes#

In the United States the food-contact route runs through 21 CFR: nylon MXD-6 is listed in 21 CFR 177.1500(a)(10)(ii) with a cyclic-monomer extraction limit of 0.5 micrograms per square inch, and the film entry is limited to 40 micrometres for food types V and IX. Item 10.3 covers non-food-contact layers in polypropylene multilayers, the entry that supports a buried scavenging layer. Our source library contains no 21 CFR entry for the oxidisable copolyester systems, and Avient states FDA food-contact status for its closure system rather than a section number. Nothing in this family is FDA approved in the sense the phrase is usually used, since food-contact substances clear through listings, threshold-of-regulation exemptions or effective food contact notifications, and every relevant 21 CFR section is mapped on FDA food contact rules.

Are Oxygen Scavengers Recyclable? EPBP, APR and the PPWR#

An oxygen scavenger is recyclable in a PET bottle only under written conditions: the European PET Bottle Platform accepts one in a clear or light-blue bottle if it stays thermally stable through 5 recycling loops and keeps non-PET content below 0.1 % of the bottle. In coloured bottles the threshold rises to 0.25 %, because colour already restricts the stream. PA-MXD6 is conditional at up to 5 wt% in clear and white three-layer bottles and 6 wt% in coloured and opaque ones, with no tie layers, while EVOH is incompatible in clear bottles and allowed up to 3 wt% in coloured multilayer. The general rules are on design for recycling.

EPBP and APR guidelines are industry design guidance, not law, but under the PPWR they are the working proxies for the design-for-recycling criteria that the Commission must set by delegated act by 1 January 2028.

The Association of Plastic Recyclers takes the same question from the other end. In the APR PET Rigid guidance an oxygen scavenger is Design Preferred if it passes the PET-CG-01 protocol after ageing under PET-P-12, and any untested additive or barrier is detrimental, which turns a missing test report into a failure. Avient states EPBP accreditation for its Oxyloop-1 grade in coloured bottle-to-bottle recycling at up to a 3 % let-down ratio, and APR Critical Guidance recognition for its closure system.

Law is closing the gap between guidance and obligation. The packaging and packaging waste regulation (PPWR), Regulation (EU) 2025/40, requires 30 % recycled content in contact-sensitive PET packaging and single-use plastic beverage bottles from 1 January 2030, 10 % in other contact-sensitive plastic packaging and 35 % in other plastic packaging, rising to 50 % for contact-sensitive PET in 2040, with design-for-recycling criteria due by delegated act by 1 January 2028. The consequence is direct: a scavenging system that contaminates the bottle stream reduces the recyclate a producer needs for its own target, and the food-contact recyclate rules are on recycled plastics regulations.

Who Makes Oxygen Scavengers? Suppliers and Trade Names#

The oxygen scavenger business splits into two groups: the additive and masterbatch houses that sell scavenging concentrates for the bottle wall or the closure, and the resin producers that sell the oxidisable barrier polymer itself. Avient, headquartered in Avon Lake, Ohio and listed on the NYSE as AVNT, sits in the first group with the ColorMatrix line, took its present name after buying the Clariant masterbatch business in 2020 for about USD 1.6 billion, and reported revenue of USD 3.26 billion in 2025 in its SEC filings. Mitsubishi Gas Chemical sits in the second group as the producer of nylon-MXD6 under the MX-Nylon name, and it is a different company from Mitsubishi Chemical. Company profiles are collected in the directory of plastic additive manufacturers and suppliers.

This table lists only companies and names recorded in our source library. No ranking, no market share and no endorsement is implied. The full portfolio of Avient is profiled separately.

Market size is known only for part of this family and only at second hand: Gupta's 2023 review quotes a market report predicting that inorganic iron-based scavengers expand at about 6 % a year from USD 2.2 billion in 2021 to USD 2.9 billion by 2026, a figure that excludes the PET wall and closure technologies, and segment data are on plastic additives market.

Complete List of Oxygen Scavenger Substances#

Three substance pages carry the chemistry of this family: the oxidisable barrier polymer nylon-MXD6 and the two cobalt carboxylates used to catalyse it. The table lists each substance with its CAS number, its role in a scavenging system and its European food-contact position, which differ enough between the two catalysts to decide which one a fatty food allows. Reduced iron powder has no separate page by design, because the family page for iron systems covers it in full.

Reduced iron powder (CAS 7439-89-6) has no separate substance page; it is covered by the iron family page. Calcium oxide, titanium nitride, antimony tin oxide, copper hydroxide phosphate, Nylostab S-EED and the carbodiimides are listed under this family in the page inventory but belong to the desiccant, reheat, laser-marking and hydrolysis-stabilizer families, and are not oxygen scavengers.

Every other substance used in plastics, with its CAS number, function and regulatory status, is in the plastic additives database.

What Else Is Called an Oxygen Scavenger, and What Do People Ask About It?#

The phrase oxygen scavenger describes at least three unrelated things: a packaging additive, a boiler-water treatment chemical and a laboratory reagent, and only the first one is a plastic additive. Search behaviour follows the largest of the three rather than the most technical, so the bare head term returns water-treatment chemistry, marine and oil-and-gas products and consumer absorber packets, and the plastics meaning appears clearly only when a qualifier such as packaging, film or PET bottles is added. The chemistries overlap just enough to mislead, since sulfite appears in both the boiler and the sachet, and iron appears in both the sachet and the film, while the dose, the target and the law are different in every case. The sections below answer the questions that arrive on those other meanings, once each, and then return to the additive.

Oxygen scavengers in boiler water, oil and gas#

In a boiler, an oxygen scavenger is a water-treatment chemical such as sodium sulfite, diethylhydroxylamine, hydrazine or carbohydrazide, dosed into the feedwater to stop dissolved oxygen corroding the metal. The same chemicals appear in oil and gas production water and in marine systems for the same reason, and sodium sulfite can indeed act as an oxygen scavenger there. Nothing in that practice transfers to packaging: the chemical is dissolved in water rather than compounded into a polymer, the target is steel rather than food, and the dose is expressed in milligrams per litre of water rather than in per cent of an article. This reference does not cover boiler-water or oilfield treatment chemicals, and no dosing figure from that field appears anywhere on this page.

Are oxygen absorber sachets safe, and what do you do with them?#

An oxygen absorber sachet is a packaging insert rather than a plastic additive, and what it contains is usually the same reduced iron powder and salt activator used in scavenging films, sealed in a permeable pouch. The iron oxidises to iron oxide as the sachet does its work, which is why a spent sachet feels warm in some formats and why the contents darken. The pouch is permeable to gas and holds the powder away from the food, which is the whole difference between an insert and an additive: nothing in a sachet is compounded into the polymer, so no migration limit of Regulation (EU) No 10/2011 applies to its contents in the way it applies to an iron-loaded film layer. This reference describes what is inside the pouch because the same chemistry appears compounded into film, and it gives no handling, storage or safety advice for consumers: that guidance belongs to the food manufacturer whose product the sachet sits in, and it appears on the pack.

What is another name for an oxygen scavenger?#

An oxygen scavenger is also called an oxygen absorber, an O2 scavenger or an active oxygen barrier, and in European food-contact law it is part of an active material. The abbreviation OS appears in converter specifications for the same thing. It is not to be confused with a radical scavenger, which is a stabiliser term for a different reaction, the interruption of an autoxidation chain rather than the consumption of molecular oxygen.

What material absorbs oxygen?#

The material that absorbs the most oxygen per gram in packaging is reduced iron powder, at about 300 cm³ of oxygen per gram, but it is opaque, so clear packages use an oxidisable polymer with a cobalt catalyst instead. The three oxidisable polymers in commercial use are nylon-MXD6, a polybutadiene-segmented copolyester and polycyclooctene, each of which consumes oxygen only while a transition-metal catalyst is present in the same wall.

Cobalt, iron and the environmental questions around active packaging#

The environmental debate around oxygen scavengers is not about the oxygen: it is about the cobalt catalyst and about whether a bottle that contains a second polymer can still be recycled into a bottle. On cobalt, the five salts on the REACH Candidate List as carcinogens are the simple inorganic and short-chain salts, the carboxylate catalysts were not on that list in the compilation checked, and the notified classifications for cobalt stearate include skin sensitisation and repeated-dose toxicity with no harmonised entry verified in our sources. On recycling, the EPBP thresholds of 0.1 and 0.25 % non-PET content and the APR requirement to pass PET-CG-01 after ageing set the practical limits today, and the recycled-content obligations that start on 1 January 2030 under Regulation (EU) 2025/40 will decide which of these systems survives, because a technology that costs a producer recyclate is a technology that costs it compliance.