MSA 464033 GMD Ammonia / Methylamine Cartridge for Comfo Respirators — Box of 10

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MSA GMD Ammonia / Methylamine Cartridge Overview

The MSA GMD (Part No. 464033) is a NIOSH-approved, chemically specific cartridge designed exclusively for ammonia and methylamine vapor hazards — it uses an impregnated sorbent bed rather than standard activated carbon, and it ships in a box of 10 cartridges at $179.63 ($17.96 per cartridge). If your facility runs a cartridge-selection protocol, the GMD belongs on the shortlist any time ammonia or methylamine is the primary vapor threat and particulate loading is absent. Understanding how different filter media work helps clarify why a chemically impregnated cartridge is the correct choice here rather than a standard organic-vapor unit. Browse the full MSA Respirator Filters & Cartridges collection to compare this cartridge against every GM-series option, and see the respirator cartridge color-code chart for NIOSH color-band reference across manufacturers.

Where the MSA GMD Fits in Respirator Selection

Confirm the hazard before selecting this cartridge: the GMD is appropriate when ammonia or methylamine is the sole vapor hazard and airborne concentrations are below the IDLH threshold (IDLH for ammonia is 300 ppm; for methylamine, 100 ppm). The MSA GMD carries an Assigned Protection Factor (APF) of 10 under OSHA 29 CFR 1910.134 when used on a properly fit-tested half-mask. That means it is suitable for exposures up to 10× the applicable PEL or TLV — confirm with your industrial hygienist that concentrations fall within that band. If particulate co-hazards such as fertilizer dust or ammonia mist are also present, step up to the MSA GMD-P100 combination cartridge. If your site has mixed acid-gas and ammonia exposure, evaluate the MSA GME multi-gas cartridge or the MSA GME-P100 instead. Review the complete respirator cartridge selection guide and the filter-types explained guide for a decision framework that covers all hazard categories.

Who Should Buy the MSA GMD Ammonia / Methylamine Cartridge?

Buy the MSA GMD if:

• You already own a Comfo Classic, Comfo II, or Advantage 200 LS half-mask and need NIOSH-approved ammonia/methylamine coverage.
• Your IH assessment confirms ammonia or methylamine as the primary vapor hazard with no significant particulate fraction.
• You want chemical-specific protection at a lower per-cartridge cost than combination cartridges — $17.96 each versus combination units.
• You work in wastewater treatment, commercial refrigeration, cold storage, livestock facility management, or fertilizer distribution.
• Your facility requires cartridge-specific NIOSH approval documentation for 42 CFR Part 84 compliance records.

Do not buy the MSA GMD if:

• Particulate hazards (dust, aerosols, fume) are co-present — use the MSA GMD-P100 instead.
• You need organic vapor or acid gas coverage alongside ammonia — use the MSA GME multi-gas cartridge.
• You own an MSA Advantage 200, 290, 420, or 1000 half-mask — those use the Advantage snap-on mount, not the GM bayonet. See MSA half-mask respirators to verify your mask series before ordering.
• Concentrations are at or above IDLH — a supplied-air respirator or SCBA is required.
• You use a full-face MSA respirator on the Advantage platform — check the MSA full-face mask respirator collection for compatible cartridges.

What Does the MSA GMD Protect Against?

The GMD cartridge uses a chemically impregnated sorbent bed approved under NIOSH 42 CFR Part 84 for the following hazards:

What the MSA GMD Does NOT Protect Against

• Particulates — no filter media; for dust, mist, or aerosol co-hazards use the MSA GMD-P100 combination cartridge
• Organic vapors — standard solvents, hydrocarbons, and VOCs are not captured by the impregnated sorbent; use the MSA GMA organic vapor cartridge for those hazards
• Acid gases — chlorine, hydrogen chloride, sulfur dioxide require the MSA GMB acid gas cartridge or a combination unit
• Combined OV + acid gas + ammonia — the MSA GME multi-gas cartridge covers this spectrum
• Mercury vapor — requires the MSA Mersorb P100 mercury vapor cartridge
• Iodine and radioiodine — requires the MSA GMI iodine P100 cartridge

Best Applications for the MSA GMD Cartridge

Wastewater Treatment and Utility Operations

Ammonia is a routine byproduct at wastewater treatment plants — from digester headspace to chemical feed areas — and operators pulling filter media, inspecting wet wells, or handling anhydrous ammonia feed systems rely on cartridges rated specifically for this hazard. The MSA GMD paired with a Comfo II or Comfo Classic half-mask provides documented APF 10 protection in routine maintenance and inspection tasks where concentrations are confirmed below IDLH. Consult the cartridge selection guide to build out your facility's respiratory program.

Commercial Refrigeration and Cold Storage

Industrial refrigeration systems that use anhydrous ammonia (R-717) as refrigerant require workers to carry appropriate respiratory protection for leak response, routine inspection, and preventive maintenance tasks. The GMD is the correct cartridge for ammonia-specific vapor control in these applications. When maintenance tasks also generate compressor oil mist or other particulates, step up to the GMD-P100 combination cartridge.

Fertilizer Distribution and Agricultural Operations

Anhydrous ammonia handling at fertilizer terminals, nurse tanks, and application equipment creates concentrated ammonia vapor exposure risk. The GMD addresses the vapor component; when dusts from granular fertilizers are simultaneously airborne, add the P100 layer with the GMD-P100 variant. See the full MSA filter and cartridge collection to compare available protection levels for agricultural environments.

Chemical Manufacturing and Pharmaceutical Processing

Methylamine is a key intermediate in pharmaceutical synthesis, agrochemicals, and specialty chemical manufacturing. Workers in these environments who need a Comfo-platform-compatible methylamine cartridge will find the GMD is one of the few NIOSH-approved cartridges explicitly rated for this compound. Review how sorbent impregnation differs from activated carbon beds when specifying protection for reactive amines.

MSA GMD Pros and Cons

Compatible MSA Respirators

The MSA GMD uses a threaded bayonet (quarter-turn) mount — the Comfo-platform connection system. It is not compatible with the MSA Advantage snap-on connection used on the Advantage 200, 290, 420, and 1000 series. Verify your mask series before ordering.

Browse the MSA half-mask respirator collection and the MSA full-face mask respirator collection to confirm your mask's connection type before ordering cartridges.

MSA GMD vs Other MSA Filters and Cartridges

All cartridges below use the same GM bayonet mount and are sold within the MSA Respirator Filters & Cartridges collection. Choose based on your specific hazard profile.

MSA GMD vs MSA GMD-P100

The MSA GMD-P100 is the direct upgrade from the GMD — it combines the identical impregnated sorbent bed for ammonia and methylamine with an integrated P100 particulate filter layer. Choose the GMD when your air-monitoring data confirms no measurable particulate fraction; choose the GMD-P100 whenever aerosols, fertilizer dust, ammonia mist, or any other airborne particles are present. The GMD is the lower-cost option per cartridge; the GMD-P100 eliminates the need for a separate prefilter and provides one-product coverage for combined hazard environments. Both use the same GM bayonet mount.

MSA GMD vs MSA GME Multi-Gas Cartridge

The MSA GME multi-gas cartridge covers organic vapors, acid gases, and ammonia/methylamine in a single unit — the broadest vapor-coverage option in the GM series without a particulate layer. If your facility has mixed chemical exposures (for example, ammonia alongside chlorine or organic solvent vapors), the GME is a more practical choice because a single cartridge covers the spectrum. The GMD is the correct selection when ammonia or methylamine is the sole vapor hazard, since chemical-specific cartridges can offer a better balance of capacity and cost when the hazard class is unambiguous. Consult the filter-types guide for a breakdown of multi-gas versus single-hazard cartridge tradeoffs.

MSA GMD Quick Answers

What is the MSA GMD cartridge used for?

The MSA GMD (Part No. 464033) is a NIOSH-approved cartridge for ammonia and methylamine vapor protection, designed for use on MSA Comfo-platform half-masks in environments such as wastewater treatment, commercial refrigeration, fertilizer handling, and chemical manufacturing where these specific vapors are the primary hazard.

Does the MSA GMD filter dust or particles?

No. The MSA GMD is a vapor-only cartridge with no particulate filtration. When particulates such as fertilizer dust, ammonia aerosol mist, or other airborne solids are present alongside ammonia vapor, the correct product is the MSA GMD-P100 combination cartridge, which adds a P100 filter layer.

What respirators fit the MSA GMD cartridge?

The MSA GMD uses a threaded bayonet (quarter-turn) mount compatible with the MSA Comfo Classic (Hycar and Silicone), Comfo II, and Advantage 200 LS half-masks. It is not compatible with Advantage 200, 290, 420, or 1000 series respirators, which use a different snap-on connection system.

How many cartridges come in a box?

The MSA GMD is sold in a box of 10 cartridges (Part No. 464033) at $179.63, which works out to $17.96 per cartridge. This pack size suits team-level respiratory protection programs and facility stocking requirements.

What protection factor does the MSA GMD provide?

When used on a properly fit-tested half-mask respirator, the MSA GMD provides an Assigned Protection Factor (APF) of 10 under OSHA 29 CFR 1910.134, meaning it is suitable for airborne concentrations up to 10 times the applicable permissible exposure limit (PEL) or threshold limit value (TLV). Your industrial hygienist must confirm that measured concentrations remain within this band.

Is the MSA GMD NIOSH-approved?

Yes. The MSA GMD is NIOSH-approved under 42 CFR Part 84 for ammonia and methylamine vapor service. The NIOSH approval confirms that the cartridge meets federal efficacy standards for the stated hazard classes when used on approved respirator platforms.

How do I know when to replace the MSA GMD cartridge?

The MSA GMD does not have an end-of-service-life indicator (ESLI). Replace cartridges on a scheduled change-out program established by your industrial hygienist based on contaminant concentration, work duration, temperature, and humidity. Cartridges should also be replaced immediately if ammonia odor is detected through the respirator, as this indicates sorbent saturation.

MSA GMD Ammonia / Methylamine Cartridge Specifications

Helpful Buying Guides

• How to Choose a Respirator Cartridge — Complete Selection Guide
• Respirator Filter Types Explained — Particulate, Vapor, and Combination
• Respirator Cartridge Color-Code Chart — NIOSH Color Band Reference
• Organic Vapor vs P100 — When to Use Each Filter Type
• Best Respirator for Silica Dust 2026 — Buyer's Guide
• Best Respirator for Welding Fumes — Top Picks and Selection Tips

MSA GMD Ammonia / Methylamine Cartridge — Frequently Asked Questions

Can I use the MSA GMD on my MSA Advantage 200 half-mask?

No. The Advantage 200 (and 290, 420, 1000 series) uses a snap-on mount that is mechanically different from the GM bayonet connection on the GMD. Mounting the wrong cartridge to an incompatible respirator creates a leak path that defeats respiratory protection. If you own an Advantage-series mask, check the MSA Respirator Filters & Cartridges collection for Advantage-compatible options.

Does the MSA GMD protect against hydrogen sulfide (H₂S)?

No. The GMD sorbent bed is engineered specifically for ammonia and methylamine — it is not NIOSH-approved for hydrogen sulfide. H₂S requires a cartridge with acid gas approval; the MSA GMB acid gas cartridge or a combination unit such as the MSA GME multi-gas cartridge are appropriate choices for H₂S environments.

How many cartridges does a worker need per shift?

Cartridge consumption depends on ammonia concentration, temperature, humidity, and work duration. Your industrial hygienist must establish a written change-schedule as required by OSHA 29 CFR 1910.134(d)(3)(iii)(B). In moderate-exposure, short-duration tasks a single pair of cartridges per shift is common, but there is no universal rule. Always follow your facility's written program.

Can I add a prefilter to the MSA GMD for dust protection?

The MSA GMD is a vapor-only cartridge with no integral prefilter attachment point for P100 media. When both ammonia vapor and particulates are present, the correct product is the MSA GMD-P100 combination cartridge, which has the P100 layer built in.

Is the GMD cartridge rated for chlorine gas?

No. Chlorine is an acid gas, and the GMD sorbent is not approved for acid gases under NIOSH 42 CFR Part 84. For chlorine or other acid gas hazards, use the MSA GMB acid gas cartridge or, for combined chlorine and ammonia exposure, the MSA GME multi-gas cartridge.

What is the shelf life of an unopened MSA GMD cartridge?

MSA impregnated cartridges have a manufacturer-stated shelf life when stored unopened in original packaging under recommended conditions (cool, dry environment away from contaminants). Check the lot date code printed on the cartridge or box and follow MSA's published storage guidance. Do not use cartridges past their marked expiration date.

Does the GMD protect against trimethylamine or other higher amines?

The NIOSH approval for the GMD covers ammonia and methylamine specifically. Other amines such as trimethylamine, dimethylamine, or ethylamine are not explicitly included in the 42 CFR Part 84 approval designation for this cartridge. Consult MSA Safety's technical team and your industrial hygienist before using the GMD for amine compounds beyond the two listed hazard classes. For broader chemical coverage, evaluate the MSA GME multi-gas cartridge.

How do I perform a seal check with the MSA GMD installed?

With the GMD cartridges installed on your Comfo-platform mask, perform a negative-pressure user seal check: block the cartridge inlet openings with your palms and inhale gently — the facepiece should collapse slightly and hold without air leaking in at the face seal. Alternatively, perform a positive-pressure check by blocking the exhalation valve and exhaling gently. Any leakage at the facepiece indicates a poor seal requiring adjustment or a different size mask.

Can the GMD be reused across multiple shifts?

Cartridges can be reused across multiple shifts provided the change schedule established by your industrial hygienist has not been reached, the cartridge has been stored in a sealed plastic bag between uses to minimize exposure to ambient contaminants, and no damage, odor breakthrough, or visible contamination has occurred. Single-use cartridges that have reached their service life must be discarded.

Does the MSA GMD include the respirator facepiece?

No. The MSA GMD is sold as a pack of 10 cartridges only. The compatible Comfo-platform facepieces — Comfo Classic, Comfo II, and Advantage 200 LS — are sold separately. See the MSA half-mask respirator collection to select and purchase a compatible facepiece.

What is the difference between the MSA GMD and the MSA 3M 6004 ammonia cartridge?

Both the MSA GMD and the 3M 6004 ammonia/methylamine cartridge are NIOSH-approved for the same hazard class, but they use entirely different connection systems. The MSA GMD uses the GM bayonet mount and only fits MSA Comfo-platform respirators. The 3M 6004 uses 3M's bayonet connection and only fits 3M 6000/7000-series respirators. These cartridges are not interchangeable between brands.

Is the MSA GMD available in a single-cartridge purchase?

The MSA GMD (Part No. 464033) is sold as a 10-pack unit. Single-cartridge purchasing is not available at WC Safety for this product. The 10-pack pricing at $17.96 per cartridge is competitive for facilities that stock cartridges for multiple workers or rotate inventory regularly.

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