Re: Need Respirator!
For sanding fiberglass what you need to be concerned with a few things regarding a respirator.
First, you need to understand how they work. I assume we are talking 1/2 mask that fit over nose and mouth. Obviously the mask itself seals to your face. It also has cartridge filters, and inflow and outflow valves. The inflow valves are located under the cartridges and only allow flow from outside through the cartridge and into the mask. They shouldn't allow flow from inside the mask back through the cartridge in order to preserve the life of the cartridge and prevent the moisture from your breath from contaminating them. There is also a similar outflow valve that allows your exhaled air out of the mask and doesn't allow air to come back in.
Next is the fit of the respirator. A respirator that doesn't seal to your face well will allow stuff in and defeat the purpose. IMO, this is more important than brand, but you also want a name brand so that you can find replacement parts and filters easily. Different brands may also afford a better fit. If there is a place where you can try one on before buying, do that. The box stores will have them in plastic bags. If you have to buy one without trying it on, perform a "fit test" once you open it. Do this by putting it on, adjusting it, and putting your palm over the outflow valve and then blowing. The mask should hold pressure and you may hear a "fart" type sound as the air finds an escape path. If you don't encounter resistance when blowing, either the inflow valves aren't working, or the mask isn't fitting properly, or is not adjusted properly. Next is to place your palms over the inflow valves and suck in. You may have to remove the cartridges to do this test. The mask should suck to your face with no leaks. If it leaks, the outflow valve could be bad, the mask doesn't fit, or isn't adjusted right. The most common problems for fit are across the bridge of the nose and facial hair. If you have a beard, shave it as the facial hair will create a leak. Masks are manufactured for "normal" face shapes and features, and if you have an face that isn't (ie: very round, very long, deep dimples, large skin creases, etc.) you may have problem finding a mask that fits correctly. Newer masks are made from very flexible materials and this isn't as much of a problem as in the past. If it is, you may want to consider spending more money for a full face respirator.
Finally, the cartridge which does the actual filtering of the air. For sanding, a particulate filter is needed. I would suggest looking for a "P100" cartridge as this will have a very effective particulate filter. It will probably come with an organic cartridge too. For sanding, the organic cartridge isn't a concern, but most times that is the best option for getting something with a particulate filter as well because they come as a single combination unit in many cases. The P100 designation means it will filter 99.97% of airborne particles.
Finally, a pet peeve of mine. Store your respirator properly. To maintain their life, the cartridges should be stored in a sealed plastic bag and the same for the mask. Also store them out of direct sunlight. Clean the mask with a mild detergent, and replace the cartridges as needed. I use new cartridges for each new paint job I do. For sanding and particulate only use, I will use the old P100 filters, but I always use a new one for painting.
It is your health. Don't cheap out, but you should be able to get a decent name brand respirator like AOSafety, or 3M for about $20 without cartridges and the cartridges should be about $20 for the P100. If you want to upgrade you can look into full silicone masks as opposed to natural rubber. I have seen AOSafety in the box stores.
Hope this helps
