MSA GMI/P100 Respirator Cartridge — Radioiodine/P100 (MSA Comfo)

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Read our MSA GMI/P100 review for the detailed review.

MSA GMI/P100 Respirator Cartridge Overview

The MSA GMI/P100 is a NIOSH-approved combination cartridge for MSA Comfo respirators that protects against radioiodine AND airborne particulate in one unit. The built-in P100 filter captures at least 99.97% of particles, so the MSA GMI/P100 covers gas plus dust without a separate prefilter. It is intended for radioiodine and radioactive methyl iodide, as found in nuclear power and isotope facilities. Start with the cartridge selection guide, the organic vapor vs P100 guide and the color chart.

As a Comfo combination cartridge it fits the MSA Comfo Classic, Comfo II, Ultra-Twin and Ultra-Elite, and belongs to the MSA respirator filters and cartridges range. Choose the gas-only GME/P100 if there is no dust; the MSA GMI/P100 when gas and particulate are both present.

Where the MSA GMI/P100 Fits in Cartridge Selection

The MSA GMI/P100 handles radioiodine and airborne particulate. If you are weighing gas-only versus combination cartridges, our filter types explained and Comfo vs Advantage guides help you decide.

Who Should Buy the MSA GMI/P100?

Buy it if your work mixes radioiodine with dust or mist on an MSA Comfo facepiece. Choose the gas-only GME/P100 if there is no dust. For a broader gas mix, see the MSA Comfo GME/P100 multi-gas cartridge.

What Does the MSA GMI/P100 Protect Against?

What the MSA GMI/P100 Does NOT Protect Against

The MSA GMI/P100 does not stop organic vapor, acid gas or ammonia. For a different gas, match the MSA cartridge to the hazard; for a broad mix use the GME/P100 multi-gas version.

No air-purifying cartridge makes a dangerous atmosphere safe. Never use the MSA GMI/P100 in an oxygen-deficient or IDLH (immediately dangerous to life or health) atmosphere, in unknown concentrations, or against gases with no warning properties — those conditions require a supplied-air or SCBA system, not a cartridge respirator. A cartridge or filter carries no assigned protection factor of its own — the APF comes from the facepiece it is fitted to: 10 for a half mask, 50 for a full facepiece (OSHA 1910.134 Table 1), which is the number that decides the highest exposure the respirator may legally be worn in. That facepiece must be fit tested before first use and at least annually, and a fit test is specific to one make, model, and size — passing on one mask does not carry over to another. Perform a user seal check every time the respirator is donned, and note that facial hair crossing the sealing surface disqualifies a tight-fitting respirator no matter how well it fit at the last test.

Best Applications

Nuclear & isotope facilities

Its distinguishing use is radioiodine and radioactive methyl iodide in nuclear power and isotope labs.

Radiation response

Where radioiodine is the controlling hazard alongside particulate.

Pros & Cons

MSA GMI/P100 vs Other MSA Cartridges

MSA GMI/P100 vs the Alternatives

How it compares to the closest MSA options:

• GMI/P100 vs GME/P100: the GMI is the radioiodine specialist; the GME/P100 covers general industrial gases.
• GMI/P100 vs GMT: the GMI targets radioiodine; the GMT targets tritium oxide — different radionuclides.
• GMI/P100 (Comfo) vs Advantage GMI: same chemistry, different facepiece system.

MSA GMI/P100 Quick Answers

Does the MSA GMI/P100 need a separate filter?

No — the P100 filter is built in; there is no prefilter or retainer to add.

Does the MSA GMI/P100 fit my MSA respirator?

It fits the MSA Comfo family; check your facepiece in the MSA half-mask and full-face ranges.

Is the MSA GMI/P100 reusable?

The cartridge is used until its gas or filter service life is reached; the respirator is reusable across many changes.

MSA GMI/P100 Specifications

Compatible MSA Respirators

The MSA GMI/P100 uses the MSA Comfo threaded-bayonet connection, so it mounts on the Comfo Classic half-mask and Ultra-Elite full-face respirators (and the Comfo II and Ultra-Twin). It is not interchangeable with the MSA Advantage series, and does not fit 3M, Honeywell North or other brands.

Helpful Buying Guides

• MSA Comfo vs Advantage
• How to choose a respirator cartridge
• MSA vs 3M respirator cartridges
• MSA vs Honeywell North cartridges
• organic vapor vs P100
• respirator cartridge color chart
• respirator filter types explained

MSA GMI/P100 Frequently Asked Questions

What does the MSA GMI/P100 protect against?

The MSA GMI/P100 is a radioiodine / P100 combination cartridge. It captures radioiodine and radioactive methyl iodide and filters at least 99.97% of airborne particulate. It does not protect against organic vapor, acid gas or ammonia.

Does the MSA GMI/P100 filter dust?

Yes. The MSA GMI/P100 has a built-in P100 filter that captures at least 99.97% of airborne particles, including oil-based mists, so no separate prefilter is needed.

Which respirators does the MSA GMI/P100 fit?

It uses the MSA Comfo threaded-bayonet connection (Comfo Classic, Comfo II, Ultra-Twin, Ultra-Elite). It does not fit the Advantage series.

What does P100 mean on the MSA GMI/P100?

P100 is the highest NIOSH particulate rating: oil-proof and at least 99.97% efficient. The MSA GMI/P100 carries a magenta P100 marking alongside its gas-class band.

Is the MSA GMI/P100 NIOSH-approved?

Yes, under 42 CFR Part 84 for its listed gases and P100 particulate. Verify against the NIOSH Certified Equipment List.

How is the MSA GMI/P100 sold?

This listing is the Each. Use ask a distributor for case pricing.

How often should I replace the MSA GMI/P100?

Replace the gas portion on your written change-out schedule, or when an end-of-service-life indicator shows it is spent. Under 29 CFR 1910.134(d)(3)(iii)(B) the change schedule must rest on objective data or an end-of-service-life indicator — odour, taste or irritation may not be the primary basis. If you can smell or taste anything through the cartridge, breakthrough has already happened: leave the area immediately and change it. Also replace it and replace when breathing through the P100 filter becomes noticeably harder.

Does the MSA GMI/P100 need a separate filter?

No. The P100 particulate filter is built in, so there is no prefilter or retainer to add.

What is the difference between the MSA GMI/P100 and the gas-only version?

Choose the gas-only GME/P100 if there is no dust; the MSA GMI/P100 when gas and particulate are both present.

What color band is the MSA GMI/P100?

The markings are magenta (p100) + radioiodine markings; confirm both your gas class and the P100 on the color chart.

Is this the genuine MSA GMI/P100 cartridge?

Yes. Buy authentic, NIOSH-approved MSA GMI/P100 cartridges through legitimate channels only.

How should I store the MSA GMI/P100?

Store it sealed in its original packaging, away from gases and dust, so neither the gas nor filter service life is used up before use.