MSA GMD Cartridge Review: Ammonia and Methylamine
MSA GMD Cartridge Review: Ammonia and Methylamine — the short answer
Short answer: The MSA GMD covers ammonia and methylamine — a pairing the GMA, GMB and GMC all exclude. The reviewed listing is live here; ammonia is IDLH at 300 ppm, and that boundary rather than the cartridge is what limits where this can be worn. Everything in this family is used under OSHA 1910.134, which means a written program, a medical evaluation before use, an annual model-specific fit test, and no air-purifying respirator in an IDLH or oxygen-deficient atmosphere.
Pros and cons
Pros
- Covers ammonia and methylamine, a pairing that general-purpose organic vapor and acid gas cartridges do not address — the GMA, GMB and GMC all exclude it.
- Threads onto the MSA facepiece range, so a program already standardized on MSA can add ammonia coverage without changing facepieces.
- A single-purpose cartridge with a clearly enumerated approval, which makes the selection decision unambiguous when your hazard assessment names ammonia.
Cons
- Ammonia is IDLH at 300 ppm, and no air-purifying cartridge may be used at or above an IDLH concentration — that boundary, not the cartridge, sets the limit of this product.
- Nothing for particulate. Dust, mist and fume need a filter, which means a combination cartridge or a separate filter on facepieces that accept one.
- Nothing for organic vapor or acid gas either — a mixed atmosphere needs a cartridge approved for the actual mixture, not this one plus an assumption.
- Requires a change schedule based on objective data; ammonia odor is not an acceptable substitute for one under 1910.134(d)(3)(iii).
Is the MSA 464033 GMD the right ammonia cartridge for wastewater, refrigeration, and fertilizer plant work?
Published · Last updated
Short answer: Yes — the MSA 464033 GMD is the specification-correct Comfo-platform cartridge for environments where the documented primary hazard is ammonia (NH₃) or methylamine (CH₃NH₂) vapor without particulate co-exposure. It is the only dedicated ammonia/methylamine-only cartridge in the MSA GM-series lineup, and OSHA respiratory protection program hierarchy supports selecting the single-hazard-specific cartridge when the documented exposure is purely alkaline gas. Upgrade to the MSA GMD-P100 when particulates are present, or to the MSA GME when chlorine, SO₂, or acid gases accompany the ammonia hazard.
The MSA 464033 GMD occupies a specialized but critical position in the MSA respirator filters and cartridges collection: it is the dedicated ammonia and methylamine vapor cartridge for the Comfo GM-series bayonet platform — the correct single-hazard selection for operations where the documented chemical exposure is alkaline gas without co-occurring acid gases, organic vapors, or particulates.
Ammonia is one of the most widely encountered industrial gas hazards in North America — present in wastewater treatment, refrigeration systems (R-717), fertilizer production, cold-storage facilities, livestock operations, and chemical synthesis. It is also one of the most chemically distinct: ammonia's alkaline character requires an impregnated sorbent formulation fundamentally different from the activated carbon beds used in OV and acid gas cartridges. Using the wrong cartridge class in an ammonia environment is not a minor specification gap — it is a compliance failure under OSHA 29 CFR 1910.134.
This review covers the 464033 GMD's impregnated sorbent design, the key differentiator versus the MSA GMD-P100 and the MSA GME, why it is the OSHA program-correct choice for a pure ammonia hazard, and the specific scenarios where a different cartridge is required.
Editorial Verdict: 4.4 / 5
The MSA 464033 GMD is the specification-correct, NIOSH-approved dedicated ammonia and methylamine cartridge for the Comfo GM-series bayonet platform. At its listed price per cartridge (its listed price/box of 10), it is the single-hazard option — a reflection of the specialized impregnated sorbent chemistry required for alkaline gas protection. It is the right cartridge when your risk assessment isolates ammonia or methylamine as the sole gas hazard. The rating of 4.4/5 reflects its precision fit for the documented hazard, the absence of ESLI, the platform limitation, and the premium per-cartridge cost relative to its sibling the MSA GMD-P100 which adds P100 at a higher price.
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Strengths
- NIOSH-approved dedicated ammonia and methylamine vapor protection — the correct single-hazard selection
- Impregnated sorbent chemistry specifically formulated for alkaline gas adsorption
- GM-series bayonet mount: positive-lock, quarter-turn engagement on Comfo Classic, Comfo II, Ultra-Elite
- Correct OSHA program selection when the documented hazard is purely NH₃ or CH₃NH₂
- Comfo-platform only — the Advantage series uses a different mount and is not compatible
- Covers both ammonia (NH₃) and methylamine (CH₃NH₂) in one cartridge
Weaknesses
- No particulate filtration — any aerosol, mist, or dust requires GMD-P100 upgrade
- No ESLI — documented change schedule required; breakthrough prediction is complex for ammonia at sub-alarm concentrations
- Highest per-cartridge cost in the GMD series at its listed price each
- No protection against organic vapors, acid gases (Cl₂, HCl, SO₂, HF), mercury, or CO
- Incompatible with Advantage 200/290/420/1000/3000 snap-on series and all 3M/Moldex facepieces
- Ammonia's IDLH (300 ppm) is relatively low — SCBA is required at higher concentrations
Who should use the MSA 464033 GMD?
- Wastewater treatment plant operators — ammonia off-gassing from biological treatment processes is a routine exposure, often without significant particulate co-hazard. The 464033 GMD is the standard-issue cartridge for this application where the hazard assessment confirms NH₃ only.
- Refrigeration technicians (R-717 systems) — industrial ammonia refrigeration is one of the highest-volume ammonia exposure scenarios in North America. R-717 system maintenance, coil defrost, and leak response all require dedicated ammonia cartridge coverage. When particulates from insulation or mechanical dust are present, upgrade to the MSA GMD-P100.
- Fertilizer plant workers — anhydrous ammonia handling, urea processing, and ammonium nitrate operations involve direct NH₃ exposure that the 464033 GMD is designed to address. Concentrations in these environments can approach or exceed IDLH (300 ppm) during upset conditions — the written program must define the concentration ceiling for APF-based use.
- Cold-storage facility personnel — ammonia refrigerant leaks are the primary acute exposure risk in cold-storage environments. The 464033 GMD is the correct response cartridge for minor leak response within the cartridge's APF ceiling. Emergency response at or near IDLH requires SCBA.
- Livestock and poultry facility workers — ammonia off-gassing from animal waste is a chronic low-level exposure with episodic high-level events during manure pit agitation. A documented change schedule and air monitoring program are essential in this application.
- Chemical synthesis workers with documented methylamine exposure — pharmaceutical synthesis, agricultural chemical production, and dye manufacturing can produce methylamine alongside ammonia. The 464033 GMD covers both alkaline gas classes in one cartridge. See the full MSA respirator filters and cartridges collection for the complete range.
What the MSA 464033 GMD does well
Purpose-built impregnated sorbent for alkaline gas adsorption
Ammonia and methylamine are alkaline gases — they cannot be effectively adsorbed by the untreated activated carbon beds used in organic vapor and acid gas cartridges. The 464033 GMD uses an impregnated sorbent — activated carbon treated with an acidic impregnant (typically phosphoric or citric acid-based chemistry) that reacts with and captures ammonia and methylamine molecules through chemisorption rather than physical adsorption alone. This is not a universal cartridge that "also catches ammonia" as a secondary capacity — it is a cartridge specifically engineered for alkaline gas capture. Using an OV-only or acid gas cartridge in an ammonia environment provides no meaningful protection.
Correct OSHA program selection for single-hazard ammonia environments
ANSI/ASSE Z88.2-2015 and the OSHA respiratory protection standard both require cartridge selection to be matched to the documented chemical exposure profile — not reflexively over-specified. When an industrial hygiene assessment isolates ammonia or methylamine as the primary vapor hazard without acid gas or OV co-exposure, the 464033 GMD is the program-correct cartridge. Selecting the MSA GME multi-gas in a pure-ammonia environment is technically compliant but introduces unnecessary cost and breathing resistance from sorbents not needed for the documented hazard profile.
Dual alkaline gas coverage: NH₃ and methylamine in one cartridge
Methylamine (CH₃NH₂) is structurally similar to ammonia and is present in several common industrial processes — pharmaceutical synthesis, agricultural chemical production, leather tanning, and certain dye manufacturing operations. The 464033 GMD's NIOSH approval covers both NH₃ and CH₃NH₂ simultaneously, eliminating the need for separate cartridges in environments with both alkaline gas species present.
GM-series bayonet platform reliability
The positive-locking, quarter-turn GM-series bayonet mount provides audible and tactile confirmation of cartridge seating — important in ammonia environments where response gear may be donned quickly. The bayonet engagement does not rely on friction retention, reducing the risk of undetected loosening during movement or physical work. Compatible with MSA Ultra-Elite full-face facepieces for APF 50 coverage in higher-concentration scenarios.
The correct choice when the hazard is purely alkaline
A critical program-design point: if the documented hazard is ammonia without chlorine, SO₂, HCl, or HF co-exposure, the 464033 GMD is the OSHA-required correct selection by hazard class. The MSA GME multi-gas cartridge covers ammonia plus acid gases plus OV — but if the IH assessment shows only NH₃, the program's written hazard evaluation should document why the correct cartridge is the GMD, not a multi-gas upgrade. Over-specification introduces unnecessary cost and may dilute program compliance documentation. See the MSA GME review for the multi-gas case.
Where the MSA 464033 GMD falls short
No particulate filtration — a frequent real-world gap
Ammonia exposure rarely occurs in a perfectly clean environment. Wastewater treatment plants generate aerosols from aeration basins; fertilizer operations produce fine particulate dust; livestock facilities have significant bioaerosol loading; refrigeration system maintenance can disturb insulation fibers. In any of these scenarios, the 464033 GMD's lack of particulate protection is a compliance gap. The MSA GMD-P100 adds P100 filtration for environments where particulate co-hazard is confirmed. See the MSA GMD-P100 review for that selection.
Ammonia change schedule complexity
This cartridge carries no end-of-service-life indicator — ammonia is detectable by odor at roughly 5 ppm, well below the 50 ppm OSHA PEL, so a wearer usually smells it long before the limit is reached, which can provide a sensory warning above the permissible level. However, OSHA 29 CFR 1910.134(d)(3)(iii) prohibits reliance on odor as a substitute for a documented change schedule. Breakthrough prediction for ammonia cartridges at sub-PEL concentrations requires careful modeling — the impregnated sorbent's capacity is concentration-dependent and more difficult to predict than activated carbon capacity for OV solvents.
Premium per-cartridge cost
At its listed price per cartridge (its listed price/box of 10), the 464033 GMD carries the highest per-unit cost among the pure-vapor GM-series cartridges. This reflects the specialized impregnated sorbent chemistry. Per-shift cost at one cartridge pair per shift is approximately Listed price — a meaningful number for high-frequency programs. Compare to the MSA GMD-P100 at its listed price each — in this case, the particulate-adding cartridge is the higher-cost option, which is the reverse of the GMC/GMC-P100 cost relationship.
No protection against acid gases, OV, mercury, or CO
Ammonia environments sometimes co-occur with acid gas hazards — chlorination-based disinfection (Cl₂) in wastewater treatment, SO₂ co-generation in fertilizer processes, and HCl in certain chemical synthesis operations. The 464033 GMD provides zero protection against these co-hazards. When the IH assessment confirms both ammonia and acid gas co-exposure, the MSA GME multi-gas cartridge is the correct upgrade path. Review the MSA GME review and the MSA GMC review for those hazard profiles.
MSA 464033 GMD vs the competitive ammonia cartridge field
How the 464033 GMD compares to directly relevant alternatives across the MSA range we cover for ammonia-involved hazard profiles:
| Spec | MSA 464033 GMD | MSA 815181 GMD-P100 | MSA 492790 GME | MSA Adv. GMD |
|---|---|---|---|---|
| Ammonia (NH₃) | ✓ | ✓ | ✓ | ✓ |
| Methylamine (CH₃NH₂) | ✓ | ✓ | ✓ | ✓ |
| P100 Particulate | — | ✓ | — | — |
| Acid Gas (Cl₂, HCl, SO₂, HF) | — | — | ✓ | — |
| Organic Vapor | — | — | ✓ | — |
| Mount Type | GM bayonet | GM bayonet | GM bayonet | MSA snap-on |
| Price per cartridge | $17.96 | $37.86 | Market | Market |
MSA GMD-P100 on Amazon MSA GME Multi-Gas on Amazon
MSA 464033 GMD — Frequently Asked Questions
Is the MSA 464033 GMD NIOSH-approved for ammonia and methylamine?
Yes. The MSA 464033 GMD carries NIOSH approval under 42 CFR Part 84 for both ammonia (NH₃) and methylamine (CH₃NH₂) vapor protection. It is the specification-correct dedicated alkaline gas cartridge for the Comfo GM-series bayonet platform. Verify the current certification on the NIOSH Certified Equipment List.
MSA 464033 GMD vs MSA 815181 GMD-P100 — which should I buy?
The 464033 GMD is the correct choice when your documented hazard is purely ammonia or methylamine vapor with no particulate co-exposure. The MSA 815181 GMD-P100 adds P100 particulate filtration but at a significantly higher per-cartridge cost. Unlike the GMC/GMC-P100 pair where the P100 variant is cheaper, here the P100 carries a real cost premium — making the particulate-free risk assessment an important cost decision. See the GMD-P100 review.
MSA 464033 GMD vs MSA GME — which should I use when both ammonia and chlorine are present?
The MSA GME is the correct choice when both ammonia and acid gases (Cl₂, HCl, SO₂) are documented in the hazard assessment. The 464033 GMD provides zero acid gas protection — using it in a chlorine co-exposure environment is a compliance failure. The GME's multi-gas sorbent covers both alkaline gas (ammonia/methylamine) and acid gas classes simultaneously. See the MSA GME review. Check MSA GME price on Amazon.
What respirators are compatible with the MSA 464033 GMD?
The 464033 GMD is compatible with GM-series bayonet facepieces: MSA Comfo Classic (Hycar and Silicone), MSA Comfo II, MSA Ultra-Twin, MSA Ultra-Elite. It is NOT compatible with Advantage 200/290/420/1000/3000 snap-on models or any 3M or Moldex facepiece.
Can I use the MSA 464033 GMD for wastewater treatment plant ammonia exposure?
Yes — the 464033 GMD is a standard-issue cartridge for wastewater treatment operators facing ammonia off-gassing from biological treatment processes, provided the hazard assessment confirms the exposure is below the cartridge's APF ceiling, no acid gas co-exposure exists, and a documented change schedule is in place per OSHA 1910.134. If aeration basin aerosols or bioaerosols are a co-hazard, upgrade to the MSA GMD-P100.
Does the MSA 464033 GMD protect against chlorine?
No. Chlorine (Cl₂) is an acid gas requiring a different sorbent chemistry from the alkaline-gas-specific impregnant in the 464033 GMD. If chlorine is present — as it is in many wastewater treatment plants that use chlorination for disinfection — the 464033 GMD must not be used alone. The correct Comfo-platform cartridge for ammonia plus acid gas co-exposure is the MSA GME. Verify the full hazard profile of your work environment before selecting a cartridge.
Can the MSA 464033 GMD be used for R-717 ammonia refrigeration system maintenance?
Yes, for maintenance tasks within the cartridge's APF ceiling where ammonia concentrations are below IDLH (300 ppm) and particulate co-hazards are absent. For high-APF coverage during R-717 system maintenance, use the 464033 GMD on the MSA Ultra-Elite full-face respirator (APF 50) rather than a half-mask (APF 10). For leak response at or approaching IDLH conditions, SCBA is required — the 464033 GMD is an air-purifying device and cannot be used in IDLH atmospheres.
How often should I change the MSA 464033 GMD cartridge?
No ESLI is present. A documented change schedule per OSHA 29 CFR 1910.134(d)(3)(iii) is required. Ammonia change schedule documentation is complex: ammonia has a detectable odor above the OSHA PEL (50 ppm TWA), but odor cannot substitute for a documented schedule. Breakthrough time modeling must account for concentration, humidity (high humidity accelerates breakthrough of impregnated sorbents), temperature, and work duration. Most programs default to end-of-shift replacement. Consult a Certified Industrial Hygienist (CIH) for formal program documentation.
What is the ammonia IDLH and does it affect cartridge selection?
NIOSH establishes ammonia's IDLH at 300 ppm. The OSHA PEL is 50 ppm TWA; the NIOSH REL is 25 ppm TWA. Air-purifying cartridges — including the 464033 GMD — are prohibited in IDLH atmospheres. On a half-mask (APF 10), the maximum use concentration is 500 ppm (10× the 50 ppm PEL) — which exceeds IDLH. In practice, IDLH governs: any scenario where IDLH conditions may be encountered requires SCBA, not an APF calculation based on PEL.
Is the MSA 464033 GMD appropriate for livestock and poultry facility workers?
Yes, for routine low-level ammonia exposure during normal operations (below OSHA PEL, with documented change schedule). However, livestock facilities present a complex hazard profile: manure pit agitation generates high ammonia spikes that can exceed IDLH; bioaerosols (endotoxins, fungi, bacteria) may be present alongside the vapor; and hydrogen sulfide (H₂S) may co-occur in confined spaces. A full site-specific hazard assessment by a CIH is essential before selecting the 464033 GMD as the program cartridge for livestock applications.
Does ammonia odor warn before the cartridge is exhausted?
Ammonia is detectable by odor at roughly 5 ppm, which is below both the NIOSH REL of 25 ppm and the 50 ppm OSHA PEL. Good warning properties do not replace a change schedule. While this provides a sensory cue, OSHA explicitly requires a documented change schedule when ESLI is absent — odor warning cannot substitute for a scheduled replacement program. Additionally, olfactory fatigue (the nose becoming desensitized to ammonia odor over time) further undermines odor as a reliable breakthrough indicator in continuous-exposure environments.
Can the MSA 464033 GMD be used in fertilizer plant operations?
Yes, for documented ammonia exposures below IDLH and the cartridge's APF ceiling, with a written change schedule. Fertilizer operations — particularly anhydrous ammonia handling and urea synthesis — produce some of the highest ambient ammonia concentrations in any industrial setting. The full-face MSA Ultra-Elite with the 464033 GMD (APF 50) provides greater protection headroom than a half-mask at the same cartridge. For upset conditions approaching IDLH, SCBA is required.
What a “multi-gas” cartridge does and does not cover
MSA’s letter codes name a specific approved list, not a general capability. The GMA is organic vapor; GMB acid gas; GMC organic vapor plus acid gas; GMD ammonia and methylamine; and the multi-gas GME and GMT cover a broader but still enumerated set. “Multi-gas” never means “any gas”. Each approval names the substances, and several carry qualifiers that matter more than the headline — MSA lists hydrogen sulfide on the GME for escape only, which is a different duty entirely from working in it.
Two limits apply no matter which letter is on the cartridge. No air-purifying cartridge removes carbon monoxide. CO is not adsorbed by the sorbents used in these cartridges, so a CO hazard is answered by ventilation, monitoring, and supplied air — never by a cartridge, whatever its multi-gas designation. And a gas or vapor cartridge does nothing for particulate: dust, fume, mist and lead need a particulate filter, which is why the combination parts exist. Read the approved-substance list for the exact part number against your air monitoring, and where the contaminant or its concentration is unknown, the answer is not a broader cartridge — it is measurement, or supplied air.
These cartridges only fit MSA facepieces
Cartridge connections are proprietary. MSA Advantage and Comfo cartridges thread onto MSA facepieces and nothing else — they do not fit 3M bayonet respirators, Honeywell North, or Moldex, and no adapter makes that combination approved. This matters beyond convenience, because a NIOSH approval covers a complete assembly: a specific facepiece with specific media. Mixing a cartridge from one manufacturer onto another’s facepiece voids the approval even if the parts physically engage, which means the respirator is no longer NIOSH-approved equipment for the purposes of OSHA 1910.134.
The practical rule when restocking: match the cartridge to the facepiece brand first, then to the hazard. Confirm the approval covering your exact combination on the NIOSH Certified Equipment List rather than from a listing, and check the letter designation printed on the cartridge against what your hazard assessment calls for. Where a program runs more than one brand of facepiece, the stores that go with each need to be physically separated — the most common way the wrong cartridge reaches a face is a shared bin.
When to change a cartridge — and why “when I smell it” is not the answer
OSHA 1910.134(d)(3)(iii) is explicit: where gas or vapor cartridges are used, the employer must either fit them with an End of Service Life Indicator approved for the contaminant, or implement a change schedule based on objective information or data that ensures cartridges are replaced before the end of their service life. Relying on odor, taste, or irritation as the primary signal is not one of the permitted options, and the reason is straightforward: many contaminants have poor warning properties, individual sensitivity varies widely, and by the time a vapor is detectable inside the facepiece the breakthrough has already happened.
Mercury is the sharpest illustration. Mercury vapor has no odor at all, which is exactly why NIOSH-approved mercury cartridges carry a colorimetric ESLI — the indicator changes color as the sorbent loads, giving the wearer a visible end-of-service signal that a nose cannot provide. Particulate filters follow a different rule: they load rather than break through, so the practical trigger is increased breathing resistance, along with damage, soiling, or contamination of the filter. Replace a particulate filter when it becomes harder to breathe through, and never wash or attempt to clean filter media.
What has to be in place before anyone wears this
A respirator is the one piece of PPE that comes with a program attached. Where respirators are required, OSHA 1910.134 obliges the employer to run a written respiratory protection program with a named administrator, and four elements govern whether the equipment on this page will actually protect the person wearing it.
Medical evaluation comes first. Under 1910.134(e), a worker must be medically evaluated — using the Appendix C questionnaire or an equivalent examination — before fit testing or use, because breathing through a respirator imposes real physiological load. Fit testing is annual and model-specific under 1910.134(f): a passing test on one make, model and size does not transfer to another, so changing facepiece or size means testing again. Facial hair that crosses the sealing surface prohibits use — this is not a grooming preference but a seal failure, and no amount of strap tension compensates. And a user seal check goes on every single donning, per Appendix B-1, which takes seconds and is the only check that happens at the moment of use. Cartridge and filter selection follows from air monitoring and a hazard assessment; where the contaminant or its concentration is unknown, the answer is not a better cartridge.
The rest of the MSA cartridge system
Because the facepiece and the media are bought separately, the useful comparisons run across the range. For single hazards we review the organic vapor GMA, the acid gas GMB, and the ammonia and methylamine GMD. For combined hazards there is the GMC and the multi-gas GME and GMT. Where dust is also present, the 815177 low-profile P100 handles particulate alone and the 815178 GMA-P100 combines organic vapor with P100 in one cartridge. The facepieces sit under MSA half mask respirators and MSA full face respirators, with the media under MSA respirator filters and cartridges.
Why trust WC Safety
WC Safety is an independent, affiliate-supported review site. We hold no inventory, sell nothing directly, and earn only from qualifying purchases made through clearly marked links — which never changes what a cartridge is approved to do. Reviews are compiled by Steven Eaton from MSA’s published technical data, the NIOSH approval record, the live listing, and the standards themselves (42 CFR 84, OSHA 1910.134) linked throughout. We hold no laboratory and run no breakthrough or fit testing, and we publish no customer-rating aggregate for any product, because we have no customers to aggregate. Where the published record is silent we say so rather than fill the gap.
Our methodology
This review is compiled from MSA’s published cartridge literature, the NIOSH approval record, the live listing, and the regulatory text. The score is an editorial judgment of approval fit, facepiece compatibility, hazard coverage and value — not a measured result, not a breakthrough test, and not an average of user ratings. Approved substances and the approval number for your exact part should be confirmed on the NIOSH Certified Equipment List and on the cartridge itself; where a listing and an approval disagree, the approval governs.
Researched and written by Steven Eaton, editor of WC Safety. Steven holds no safety certification and does not test products; this page compares what manufacturers publish, with the gaps in that record marked. Last reviewed July 2026.
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