3M™ Half Facepiece Respirator Assembly Kit 6391, Large

Who is the 6391 large kit designed for?

The 6391 is designed for users with larger facial dimensions — typically those with a wider jaw, longer chin-to-nose distance, or broader cheekbones — who find the medium 6200 facepiece in the 6291 kit leaves gaps at the chin or cheeks. A proper seal requires the facepiece to contact the face continuously around its entire perimeter. If the 6291 medium does not seal properly, the 6391 large is the appropriate choice.

What hazards do the included 2091 P100 filters protect against?

The 3M 2091 P100 filters provide at least 99.97% filtration efficiency against oil and non-oil-based airborne particles, including lead dust, asbestos fibers, silica dust, metal fumes, mold spores, and fine construction particulates. The P100 rating is the highest NIOSH particulate filter class. The 2091 does not protect against gases or vapors — if chemical gas protection is also needed, substitute with 3M combination cartridges such as the 60921 OV/P100.

Can the 6300 facepiece be used with cartridges other than the included P100 filters?

Yes. The 6300 facepiece uses the standard 3M bayonet connection and accepts all 3M 2000, 5000, 6000, and 7000 Series filters and cartridges. After the included 2091 P100 filters need replacement, the facepiece can be paired with organic vapor cartridges, combination OV/P100 cartridges, acid gas cartridges, or other 3M filter combinations appropriate for the application.

Does the 6391 kit require a fit test before use?

For workplace use under OSHA 29 CFR 1910.134, a formal fit test is required. The fit test confirms the specific respirator model and size achieves an adequate seal for the wearer. A medical evaluation is also required before workplace use. For non-occupational DIY use, a fit test is not legally required, but performing a user seal check (negative-pressure check by covering the filters and inhaling to feel for leakage) is always recommended before entering a contaminated environment.

How long will the 6300 facepiece last compared to the included filters?

The 6300 facepiece carries a lifetime warranty and is designed to last many years when properly maintained. The 2091 P100 filters are consumable — replace them when breathing resistance increases noticeably, when they are damaged or wet, or according to your facility's change-out schedule. Additional 2091 filters are sold separately in packs of 10 pairs and are widely available. The facepiece body itself rarely needs replacement unless the faceseal cracks or the headbands break.