MSA 464033 GMD Ammonia/Methylamine Cartridge Review (4.4/5)

Is the MSA 464033 GMD the right ammonia cartridge for wastewater, refrigeration, and fertilizer plant work?

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 $17.96 per cartridge ($179.63/box of 10), it carries the highest per-unit cost in the GMD family — 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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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

The NIOSH ESLI approval for ammonia cartridges is technically available but practically complex — ammonia has a distinctive above-OSHA-PEL odor threshold (odor detectable at approximately 5 ppm; OSHA PEL is 50 ppm TWA; IDLH is 300 ppm), 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 $17.96 per cartridge ($179.63/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 $35.92 — a meaningful number for high-frequency programs. Compare to the MSA GMD-P100 at $37.86 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 site's MSA inventory for ammonia-involved hazard profiles:

MSA GMD-P100 on Amazon MSA GME Multi-Gas on Amazon

MSA Comfo ammonia family: 464033 GMD vs 815181 GMD-P100

The Comfo GM-series offers two dedicated ammonia cartridges. The 464033 GMD is the vapor-only option; the 815181 GMD-P100 adds P100 particulate filtration. Unlike the GMC/GMC-P100 pair, here the P100 variant is significantly more expensive per cartridge:

• Buy the MSA 464033 GMD if your documented hazard is ammonia or methylamine vapor only, no particulate co-exposure, Comfo or Ultra-Elite GM-bayonet platform, and per-cartridge cost efficiency is a priority.
• Buy the MSA 815181 GMD-P100 if aerosols, bioaerosols, insulation fibers, fertilizer dust, or other particulates are present alongside the ammonia hazard. The per-cartridge premium ($37.86 vs $17.96) reflects the added P100 filtration layer. See the MSA GMD-P100 review.
• Buy the MSA GME if acid gases (Cl₂, HCl, SO₂) or organic vapors co-occur with the ammonia hazard. See the MSA GME review.

Shop the Comfo GMD series on Amazon → MSA 464033 GMD MSA 815181 GMD-P100

Compatible respirators for the MSA 464033 GMD

The 464033 GMD uses the MSA GM-series bayonet mount. Confirmed compatible facepieces:

• MSA Comfo Classic (Hycar) — the standard Comfo half-mask; accepts all GM-series cartridges directly. APF 10. Appropriate for ammonia exposures up to 10× the OSHA PEL (50 ppm TWA), i.e., up to 500 ppm. Note: ammonia IDLH is 300 ppm — at or above IDLH, SCBA is required regardless of APF rating.
• MSA Comfo Classic (Silicone) — silicone facepiece variant; same GM-series bayonet interface and APF 10.
• MSA Comfo II — updated Comfo half-mask; same interface. APF 10.
• MSA Advantage 200 LS — accepts GM-series bayonet via adapter. APF 10. Note: the Advantage 200 LS is listed as compatible with the GMD; verify with the current MSA compatibility documentation before deployment.
• MSA Ultra-Elite — MSA's premium full-face respirator with GM-series bayonet. APF 50. The preferred facepiece when ammonia concentrations may approach but remain below IDLH (300 ppm), requiring the higher APF margin.

Not compatible: Advantage 200 (non-LS), Advantage 290, 420, 1000, 3000 snap-on models; all 3M and Moldex facepieces. For Advantage snap-on facepieces, use the MSA Advantage GMD. See the Advantage GMD review for platform-specific guidance.

For environments where a P100 layer is needed on top of ammonia coverage, the MSA GMD-P100 replaces the 464033 GMD entirely — there is no separate pre-filter that adds P100 to the 464033 GMD's body. Note also that the MSA Low Profile P100 Particulate Filter does not combine with the 464033 GMD to add P100 protection; the GMD-P100 is the integrated solution.

Top compatible MSA respirators on Amazon → MSA Ultra-Elite Full-Face MSA Advantage 200 LS

Category context: why ammonia requires its own cartridge chemistry

The most important category concept for the 464033 GMD is that ammonia cartridges are chemically incompatible with organic vapor and acid gas cartridges — and vice versa. The chemistry explains why:

• Organic vapor cartridges (GMA series) use non-impregnated activated carbon for physical adsorption of non-polar organic solvent molecules. Ammonia's polar, alkaline character is poorly adsorbed by untreated carbon — an OV cartridge provides minimal to no protection against ammonia. See the MSA GMA.
• Acid gas cartridges (GMB series) use activated carbon impregnated with alkaline reagents to capture acidic gas molecules. Deploying an acid gas cartridge in an ammonia environment is particularly hazardous: the alkaline impregnant and the alkaline ammonia gas do not react beneficially — the cartridge provides little ammonia protection and may provide false confidence.
• Ammonia/methylamine cartridges (GMD series) use acidic impregnants that neutralize the alkaline ammonia and methylamine molecules. The 464033 GMD is purpose-formulated for this chemistry.
• Multi-gas cartridges (GME series) combine multiple sorbent types and are the correct choice when the hazard involves both ammonia and other gas classes. See the MSA GME review.

For the 3M platform in multi-gas environments including ammonia, the 3M 60926 covers ammonia alongside OV, acid gas, and P100 particulate on the 3M facepiece platform. See the 3M 60926 review. Browse the full MSA respirator filters and cartridges collection for the complete GM-series range.

Total cost of ownership: MSA 464033 GMD change schedule and per-shift economics

At $179.63 per box of 10 ($17.96 per cartridge), the 464033 GMD is the highest-cost pure-vapor cartridge in the GM-series lineup. TCO is driven entirely by change frequency, and ammonia programs typically require careful documentation:

• Per-shift pair cost: Two cartridges per shift = approximately $35.92/shift at the listed price.
• Change schedule complexity: Ammonia breakthrough time is concentration- and humidity-dependent, but ammonia's notable odor above the OSHA PEL can create false confidence. Under OSHA 1910.134(d)(3)(iii), odor alone is not an acceptable substitute for a documented change schedule. Most ammonia programs default to end-of-shift replacement; high-concentration environments (fertilizer operations, refrigeration system repairs) may require shorter intervals.
• GMD vs GMD-P100 cost decision: The MSA GMD-P100 at $37.86 each is more than twice the per-cartridge cost of the 464033 GMD. Unlike the GMC/GMC-P100 relationship (where the P100 variant is cheaper), here the P100 variant carries a significant premium. This makes the 464033 GMD the cost-correct choice when the particulate-free assessment is firmly documented.
• Storage: Impregnated sorbent cartridges are sensitive to moisture — storage in original sealed packaging is critical. Ammonia impregnants can degrade in high-humidity storage conditions faster than untreated activated carbon. Follow MSA storage guidance and rotate stock accordingly.

For OV/acid gas co-exposure reviews, see the MSA GMC review and the MSA GMC-P100 review. For a full multi-gas combination with P100 on the MSA platform, see the MSA GME-P100 review.

Final verdict: MSA 464033 GMD

The MSA 464033 GMD is the specification-correct, NIOSH-approved dedicated ammonia and methylamine cartridge for the Comfo GM-series bayonet platform. Its impregnated sorbent chemistry is specifically formulated for alkaline gas adsorption — it is not a general-purpose cartridge with ammonia coverage bolted on. When the industrial hygiene assessment documents a pure ammonia or methylamine hazard without particulate co-exposure, the 464033 GMD is the OSHA-correct single-hazard selection at the lowest cost in the GMD family.

The 4.4/5 rating reflects its precision chemistry match and compliance with single-hazard selection principles, offset by the absence of ESLI, the premium per-cartridge cost relative to OV-class cartridges, and the narrow platform compatibility.

• Buy the MSA 464033 GMD if your documented hazard is ammonia or methylamine vapor only — no particulates, no acid gas, no OV co-exposure — on a Comfo or Ultra-Elite GM-bayonet platform.
• Buy the MSA 815181 GMD-P100 if bioaerosols, insulation fibers, fertilizer dust, or other particulates co-occur with the ammonia hazard. See the GMD-P100 review.
• Buy the MSA GME if acid gases (chlorine, SO₂, HCl) or organic vapors co-occur with the ammonia exposure. See the GME review.
• Buy the MSA Advantage GMD if your facepiece is an Advantage snap-on model (200, 290, 420, 1000, 3000). See the Advantage GMD review.

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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 ($37.86 vs $17.96). 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, and the MSA Advantage 200 LS via bayonet adapter. 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 has a detectable odor at approximately 5 ppm — well above safe levels but below the 50 ppm OSHA PEL. 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.

Why is the MSA 464033 GMD more expensive than the MSA GMC OV/AG cartridge?

The impregnated sorbent chemistry required for ammonia and methylamine adsorption is more costly to produce than the activated carbon beds used in OV and acid gas cartridges. Impregnation processes require controlled chemical treatment of the carbon substrate and quality verification of the reactive loading — both of which add manufacturing cost. The 464033 GMD at $17.96 per cartridge reflects this chemistry premium. It is also worth noting that the MSA 815180 GMC-P100 at $7.75 per cartridge — a triple-combination cartridge — costs substantially less, which underscores that price in the GM-series is driven primarily by cartridge chemistry, not complexity alone.

Is the MSA 464033 GMD approved for methylamine in pharmaceutical manufacturing?

The 464033 GMD carries NIOSH approval for methylamine (CH₃NH₂) as a gas class. For pharmaceutical synthesis environments where methylamine is the documented primary vapor hazard, the 464033 GMD is the specification-correct cartridge. However, pharmaceutical synthesis environments typically involve multiple chemical exposures — OV solvents, other amines, and potentially particulate API. A full hazard assessment is required to confirm that the GMD alone covers the documented exposure profile before single-cartridge deployment.

What should I do if I smell ammonia while wearing the MSA 464033 GMD?

If ammonia odor is detected while wearing the 464033 GMD, immediately leave the contaminated area. Odor breakthrough signals that the cartridge's sorbent capacity is approaching exhaustion, the concentration exceeds the cartridge's effective range, or the facepiece seal has been compromised. Do not remain in the area to investigate — exit, replace the cartridge pair, perform a user seal check, and re-evaluate the concentration versus the cartridge's APF ceiling before re-entry. Report the breakthrough event to the safety program administrator for change schedule revision.