Can you use a PAPR in a confined space or a tank?
No. An air-purifying respirator cleans the air around you, so that air has to be breathable to begin with. Below 19.5% oxygen, or in an explosive atmosphere, the answer is supplied air, not a filter.
This is the distinction that matters most in this whole category, and it is genuinely misunderstood.
Air-purifying means what it says: it takes the air in the room and cleans it. If the room does not have enough oxygen in it, cleaning it changes nothing. A powered unit does not rescue this either, because the blower moves the same deficient air, only faster.
Supplied-air respirators are a different category entirely. They feed you air from a compressor or a cylinder, and that is what confined-space work calls for.
The manual states it plainly: not for use in oxygen-deficient atmospheres below 19.5% oxygen, or in explosive atmospheres.
For woodworking this rarely arises, because a shop is not a confined space. It matters if you also do tank work, silo work, or anything running under a permit system, because the respirator that is right for your sanding is emphatically not the one for that.
Related questions
I have a beard and I wear glasses. Is there anything that works? Do I actually need a respirator for woodworking, or is that overkill? Does the carbon pre-filter mean it handles fumes? Should I spend on dust collection or a respirator first?The Breathie Thingy
A powered air-purifying respirator for woodworkers. $499 for the first 30 units of each batch, including a spare filter kit.
See the current batch