MSA 815184 GMI Iodine Vapor / P100 Cartridge for Comfo Respirators — Box of 6

MSA GMI Iodine Vapor / P100 Cartridge Overview

The MSA GMI (part number 815184) is a dual-protection cartridge rated for radioactive and non-radioactive iodine vapor — including elemental iodine (I₂) and methyl iodide (CH₃I) — combined with NIOSH P100 particulate filtration at 99.97% efficiency. It ships as a box of 6 cartridges at $185.56 ($30.93 per cartridge), making it a specialty item priced for institutional and industrial buyers rather than casual users. The GMI threads onto the bayonet mount shared by all MSA Comfo-platform respirators and is the only cartridge in the MSA Comfo filter lineup purpose-designed for iodine and radioisotope environments.

Before selecting this cartridge, confirm the hazard class. Iodine-vapor exposure in nuclear medicine and radiopharmacy is distinct from organic vapor or acid-gas hazards — if you work with general solvents or chlorine instead, the MSA GMA/P100 or MSA GMB/P100 are the correct choices. For an overview of how to match hazard classes to cartridge types, see the respirator filter types explained guide and the cartridge selection guide.

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Where the MSA GMI Fits in Respirator Selection

Cartridge selection must start with the confirmed hazard class — not the respirator you already own. Iodine vapor, particularly radioactive iodine-131 used in nuclear medicine and nuclear power applications, requires a sorbent medium that reacts with and retains iodine. The GMI uses activated carbon impregnated with specific chemical reagents that bond elemental iodine and methyl iodide rather than simply adsorbing them the way standard organic-vapor charcoal does. The P100 layer then captures radioactive particulate above 0.3 microns at 99.97% efficiency.

This places the GMI in a narrow but non-negotiable specialty tier. Workers in nuclear power plant maintenance who handle radioactive iodine-laden coolant gases, nuclear medicine techs who handle I-131 vials, and radiopharmacy compounding staff are the primary audience. If your hazard profile includes multiple gas classes — for instance iodine plus organic vapors — consult your industrial hygienist, as a single-cartridge solution may not address the full exposure. The cartridge selection guide and the filter types guide both cover multi-hazard scenarios in detail.

Within the MSA Comfo cartridge family, the GMI sits above the single-gas cartridges (GMA, GMB, GMD) and the multi-gas options (GME, GMT) in terms of specialization. If your site uses a different respirator platform, review whether your facepiece takes bayonet-mount cartridges before purchasing — the GMI will not thread onto Advantage-series snap-on ports or 3M bayonet respirators.

Who Should Buy the MSA GMI Iodine / P100 Cartridge?

Buy the GMI if you:

• Work in nuclear medicine, radiopharmacy, or nuclear power and handle radioactive or non-radioactive iodine vapor as a documented site hazard
• Already own or are buying an MSA Comfo full-face respirator (Ultra-Elite, Ultra-Twin) or an MSA Comfo Classic / Comfo II half-mask with bayonet mounts
• Need simultaneous P100-grade particulate protection alongside the iodine sorbent — both in one cartridge, one qualification, one change-out schedule
• Procure respirator consumables for an institutional safety program where NSN/part-number traceability matters (part 815184 appears on government and nuclear utility qualified product lists)
• Require NIOSH-approved protection confirmed for methyl iodide (CH₃I), not just elemental iodine

Don't buy the GMI if you:

• Face organic vapor hazards (solvents, paints, pesticides) — the MSA GMA/P100 cartridge is the correct choice
• Face acid gas hazards such as chlorine, hydrogen chloride, or sulfur dioxide — use the MSA GMB/P100
• Need combined organic vapor plus acid gas protection — the MSA GMC/P100 covers that combination
• Own an MSA Advantage-series half-mask (200, 290, 420, 1000) — that platform uses snap-on filters, not bayonet cartridges
• Work with mercury vapor — the MSA Mersorb/P100 is purpose-built for mercury and is a separate cartridge chemistry
• Need ammonia or methylamine protection — select the MSA GMD/P100 instead

What Does the MSA GMI Protect Against?

The table below maps the GMI's NIOSH-rated protection to specific hazard classes and buyer guidance:

What the MSA GMI Does NOT Protect Against

• Organic vapors (solvents, VOCs): The GMI's impregnated carbon is optimized for iodine chemistry, not general organic vapor adsorption. Use the MSA GMA cartridge for solvent environments.
• Acid gases (chlorine, HCl, SO₂): Acid-gas sorbents are not present in the GMI formulation. The MSA GMB cartridge covers this class.
• Mercury vapor: Mercury requires a separate Mersorb sorbent — see the MSA Mersorb/P100.
• Ammonia and methylamine: The MSA GMD cartridge is required for these bases.
• Carbon monoxide, hydrogen sulfide: These require supplied-air (SCBA) or specific canister chemistries not present in the GMI.
• Gases below the minimum detectable odor threshold in oxygen-deficient atmospheres: Air-purifying respirators cannot warn the wearer of hazardous concentrations in low-oxygen conditions.

Best Applications for the MSA GMI Cartridge

Nuclear Medicine and Radiopharmacy

Nuclear medicine technologists who handle I-131 (sodium iodide) capsules, solutions, or dose-preparation procedures are the core user for this cartridge. Methyl iodide off-gassing during vial opening is the primary inhalation pathway, and the GMI's impregnated-carbon sorbent is specifically rated for CH₃I capture. Pair with a full-face MSA Comfo respirator when splash risk also exists. Consult your radiation safety officer for site-specific cartridge-change schedules based on I-131 activity levels.

Nuclear Power Plant Maintenance

Reactor coolant system maintenance, fuel-handling operations, and containment entries in BWR/PWR plants can produce radioactive iodine in the off-gas stream. The GMI's dual iodine/P100 rating supports respiratory protection programs where both vapor and particulate radioiodine are present. Nuclear utility safety programs frequently specify bayonet-compatible Comfo respirators as plant-issued equipment, making the GMI a direct drop-in for existing facepiece inventories.

Isotope Production Laboratories

Commercial isotope production facilities and university research reactors that produce, handle, or ship radioactive iodine compounds need a cartridge rated for both elemental and organic iodine forms. The GMI's NIOSH approval specifically covers both I₂ and CH₃I, making it suitable for hot-cell and fume-hood work where volatile iodine species may be present. See the filter types guide for a breakdown of how sorbent cartridge chemistries differ from standard OV carbons.

Industrial Iodine Chemical Manufacturing

Non-radioactive iodine vapor is also a significant inhalation hazard in pharmaceutical API synthesis, iodine-based disinfectant manufacturing, and photographic chemical production. The GMI protects against non-radioactive iodine with the same NIOSH-approved sorbent chemistry as for radioactive iodine — making it the correct choice in these industrial settings as well. Consult the cartridge selection guide to confirm the GMI is appropriate for your specific process concentrations and exposure limits.

Pros and Cons

Compatible MSA Respirators

The GMI uses the MSA Comfo-series threaded bayonet mount. It is not compatible with MSA Advantage snap-on ports or any other manufacturer's bayonet standard.

If you need an MSA full-face respirator to pair with the GMI, see the full collection. For half-mask options on the Comfo platform, browse MSA half-mask respirators.

MSA GMI vs Other MSA Comfo Cartridges

All cartridges below use the same MSA Comfo threaded bayonet mount. Select by hazard class, not by respirator fit.

MSA GMI vs MSA GME/P100 — Which Multi-Hazard Option Is Right?

The MSA GME/P100 multi-gas cartridge is the most common alternative buyers compare to the GMI when they work in environments with uncertain or mixed chemical hazards.

MSA GMI vs MSA Mersorb/P100 — Specialty Cartridge Comparison

Both the GMI and the MSA Mersorb/P100 mercury cartridge are specialty impregnated-carbon cartridges for hazards that standard OV carbon does not capture effectively. Workers sometimes ask about these two together when working in facilities that handle both iodine-based reagents and mercury-containing equipment.

MSA GMI Quick Answers

Does the MSA GMI protect against radioactive iodine?

Yes. The MSA GMI Iodine Vapor / P100 cartridge is NIOSH-approved for both radioactive and non-radioactive forms of iodine vapor, including elemental iodine (I₂) and methyl iodide (CH₃I). The activated carbon in the cartridge is impregnated with specific reagents that chemically react with and retain these iodine species rather than relying solely on physical adsorption. The integrated P100 layer additionally captures radioactive particulate aerosols at 99.97% efficiency.

What MSA respirators does the GMI cartridge fit?

The GMI uses the MSA Comfo-series threaded bayonet mount and is compatible with all Comfo-platform respirators: the Ultra-Elite full-face, Ultra-Twin full-face, Comfo Classic half-mask, and Comfo II half-mask. It does not fit MSA Advantage-series respirators (200, 290, 420, 1000), which use a snap-on filter attachment, or any 3M respirator.

How many cartridges come in a box and what is the per-unit cost?

The MSA GMI is sold in a box of 6 cartridges at $185.56, which works out to $30.93 per cartridge. Most nuclear safety programs procure by the box to ensure availability for scheduled change-outs and minimize purchasing events.

Is the GMI the same as a standard organic vapor cartridge?

No. Standard organic vapor cartridges (like the MSA GMA) use activated carbon that adsorbs organic molecules through physical surface attraction. The GMI uses a reagent-impregnated carbon that chemically reacts with iodine species — a completely different mechanism. Using a standard OV cartridge in an iodine environment is not NIOSH-compliant and may provide inadequate protection for I₂ and CH₃I.

How do I know when to change the MSA GMI cartridge?

Change-out schedules for the GMI in radioactive iodine environments cannot be determined by odor-threshold detection alone because the sorbent reacts chemically with iodine — you cannot rely on smell as a warning. In nuclear medicine and nuclear power applications, change-out intervals should be established by a qualified health physicist or industrial hygienist based on measured or estimated air concentrations, cartridge manufacturer capacity data, and regulatory requirements. End-of-service-life indicators (ESLI) are not present on the GMI; schedule-based replacement is the standard practice.

Can I use the MSA GMI for general-industry chemical exposures?

Only if iodine vapor (I₂ or CH₃I) is the confirmed primary hazard. The GMI is not rated for organic vapors, acid gases, ammonia, or mercury. If your workplace has multiple chemical hazards, the MSA GME/P100 multi-gas cartridge may be a better fit — but confirm the correct selection with a cartridge selection guide or a qualified industrial hygienist.

What is the NIOSH part number and MSA part number for the GMI?

The MSA part number is 815184. Buyers procuring against government or utility qualified product lists should confirm NIOSH approval number documentation with MSA Safety directly or through their authorized distributor, as NIOSH TC numbers for specialty cartridges are not published on retail product pages.

MSA GMI Iodine / P100 Cartridge Specifications

Helpful Buying Guides

• How to Choose a Respirator Cartridge — Complete Selection Guide
• Respirator Filter Types Explained — P100, OV, Acid Gas, and Specialty
• Organic Vapor vs P100 — When to Use Each Filter Type
• Respirator Cartridge Color Chart — NIOSH Color-Code Reference
• Best Respirator for Silica Dust (2026 Guide)
• Best Respirator for Welding Fumes — Buyer's Guide
• MSA Respirator Filters and Cartridges — Full Collection
• 3M Respirator Filters and Cartridges — Compare Brands

MSA GMI Iodine / P100 Cartridge — Frequently Asked Questions

Can the MSA GMI be used for iodine exposure in a non-nuclear industrial setting?

Yes. The GMI is NIOSH-approved for non-radioactive iodine vapor as well as radioactive iodine. Workers in pharmaceutical API synthesis, iodine disinfectant production, photographic chemical manufacturing, and similar industries who face elemental iodine or methyl iodide exposure can use the GMI on MSA Comfo-platform respirators. Confirm that iodine is the primary gas-phase hazard and that concentrations are within NIOSH-rated limits for air-purifying respirator use.

Does the GMI cartridge fit on a half-mask or does it require a full-face respirator?

The GMI fits both half-mask and full-face respirators in the MSA Comfo platform. The Comfo Classic and Comfo II half-masks both accept the bayonet cartridge mount. Full-face models (Ultra-Elite, Ultra-Twin) also accept it and provide a higher assigned protection factor (APF 50 vs APF 10 for half-mask). For radioactive iodine applications, your radiation safety program may require the higher protection factor of a full-face respirator — consult your health physicist.

How many GMI cartridges does one full-face MSA respirator use?

MSA full-face Comfo-platform respirators (Ultra-Elite, Ultra-Twin) use two cartridges simultaneously — one on each side of the facepiece. Half-mask Comfo respirators (Comfo Classic, Comfo II) also use two cartridges. A box of 6 cartridges therefore yields 3 complete cartridge sets (one change-out for three workers, or three change-outs for one worker).

Is the MSA GMI available individually, or does it only come in a 6-pack?

The standard retail and institutional packaging for the MSA GMI is a box of 6 cartridges (part 815184) at $185.56. Individual cartridges are not typically sold separately through safety distributors. The 6-pack format is aligned with institutional procurement cycles and ensures that replacement cartridges are available for full change-out sets without partial boxes.

Can the GMI be used in a nuclear power plant respirator protection program?

The GMI is used in nuclear power plant maintenance and outage work where radioactive iodine inhalation is a documented hazard. However, nuclear utility respiratory protection programs are governed by 10 CFR 20 and site-specific radiation work permits. Whether the GMI is the correct cartridge for a specific plant task — versus an SCBA or supplied-air respirator — must be determined by a qualified health physicist based on air monitoring data and dose assessment. The GMI is a component of a broader radiological protection program, not a standalone solution.

What is the difference between the MSA GMI and the MSA GMA cartridge?

The MSA GMA uses standard activated carbon rated for organic vapors such as solvents, fuels, and VOCs. The GMI uses activated carbon impregnated with reagents specifically formulated to chemically capture iodine species (I₂ and CH₃I). These are different hazard ratings and are not interchangeable. Do not use a GMA cartridge in an iodine environment — it is not NIOSH-approved for that hazard class.

Does the GMI cartridge have an expiration date?

Yes — cartridges should be stored sealed in the original packaging and used before the manufacturer's stated shelf life. Impregnated carbon cartridges can lose sorbent capacity over time even when unopened if packaging is compromised. Once opened and put into service, change-out must be governed by a documented schedule based on exposure levels rather than by odor detection. Check the packaging label for the specific lot expiration date at time of receipt.

What happens if I use the wrong cartridge in an iodine environment?

Using a standard OV cartridge (such as the GMA) or a P100-only filter in an iodine vapor environment means the gas-phase iodine passes through the filter medium and reaches the wearer's breathing zone. P100 filters capture particulate but have no gas-phase sorbent capacity. This is a serious safety failure mode, particularly in radiopharmacy and nuclear medicine where even sub-TLV I-131 inhalation carries radiological dose significance. Always verify the NIOSH hazard class rating on the cartridge packaging matches your confirmed workplace hazard.

Does WC Safety offer bulk pricing on the MSA GMI for institutional orders?

WC Safety supplies safety programs for industrial and healthcare facilities. For large-volume or blanket-order pricing on the GMI (part 815184) or other MSA Comfo cartridges, contact the WC Safety team directly. Institutional buyers such as nuclear utilities, hospital radiation safety programs, and government labs often require annual supply contracts and traceability documentation.

Is the MSA GMI compatible with Moldex or 3M half-mask respirators?

No. The GMI uses the MSA Comfo-series threaded bayonet mount, which is not interchangeable with 3M's bayonet standard or with Moldex's cartridge attachment system. If you use Moldex respirators, see Moldex cartridges and filters. If you use 3M respirators, see 3M respirator filters and cartridges. Cross-brand mounting is not permitted under NIOSH approval conditions.

Can I use the GMI in a confined space?

No. The GMI is an air-purifying cartridge that cannot be used in oxygen-deficient atmospheres (below 19.5% O₂), permit-required confined spaces with unknown atmospheric conditions, or IDLH environments. A supplied-air respirator or SCBA is required for confined-space entry where the atmosphere has not been verified as safe for air-purifying respirator use. Consult OSHA 1910.134 and your site confined-space program.

Where can I read a detailed review of the MSA GMI before purchasing?

The WC Safety editorial team has published a full review of the MSA GMI Iodine / P100 cartridge covering performance specifications, application suitability, compatibility details, and how it compares to sibling cartridges in the Comfo lineup. Read the full MSA GMI product review for a comprehensive pre-purchase assessment.