Not a builder, but a fan of all you builders. Oh and I am responsible for a respirator program for a large employer.
Respirator fit is very important that is why they make different sizes. My required respirator users, myself included, have to pass a quantitative fit-test before they can wear respirators around known high or potentially high exposures. Are you wearing your respirator over facial hair? That could be a problem. A tight fit is important.
If you can get a fit test, I recommend it. Read appendix A of OSHA 1910.134 for the different methods.
http://osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9780
If not, do the best you can and follow manufacturers recommendations.
Not trying to put snores on you all, but there is important info. to know in order to protect your self from inhalation exposure. And hey your are getting a good deal. Hire a Certified Industrial Hygienist to see what they would charge you for this info. Many who are just consultants do not know a lot of the details learned by running a program. I am a CIH too, and a mountain biker for over 20 years.
For particulates you need to know filter (mechanical capture) jargon. N, P or R before 95, 99 or 100 means: N-not resistant to oil mist(as in large fab shops with lots of oil mist), P-partially resistant to oil mist, and R-resistant to oil mist. N should work for most of you. The number is the percent of efficiency as tested against 0.3 micron particles(95 is 94.99%; 99 is 98.99% and 100 is 99.99%). Welding fumes can be as small as 0.1 micron. This does not mean that 0.1 particles sail through the filter. When particles get this small, they behave much differently and are not affected by gravity as much as heavier particles. 0.3 microns is the most penetrating particle size, so it is the test standard. N95s are approved for tuberculosis and should work for all of your basic mechanical particulate generating needs. I commonly use N95 dust masks(Note these are technically respirators) Dust masks are usually single strapped and have no NIOSH rating or approval.
For welding, the N95s work, but I would use a N, R or P100 filter P100 cartridges are quite common. I use them with my dual cartridge half face. For vapors and gases you must get specific cartridges that capture via chemical capture. Organic vapor should cover most of your gas vapor contaminants. When in doubt use the best cartidge like a North Defender.
Know your contaminate form: Particulate, vapor or gas. In the respirator world, fume is a particle produced by condensation and not a vapor or gas. Metal fume is correct, gasoline fume is not. Gasoline vaporizes into a vapor. Metal fume is produced when the metal you just vaporized, with your arc, cools rapidly and condenses from a vapor to a solid particle. Note the liquid state of matter is skipped. Dry ice does the same thing in reverse...sublimation. If you read respirator cartridge info. you will see many that are for dusts, mists, fume, etc. This type of cartridge/respirator will not protect you at all from a vapor.
Two part anything (epoxy, urethane, etc.) can be particularly nasty. Be very careful of inhalation (working with no exhaust ventilation, respirator, etc). Also avoid skin contact. If you doubt me, read the Material Safety Data Sheets (MSDS). Known sensitizers can cause you to become allergic to them with enough exposure. Car painters wear(if not they should) supplied air respirators when applying such materials.
I have two auto body employees and they like the North Pancake with nuisance level OV capacity for sanding & grinding on car bodies. They work with a half face or full face dual cartridge. Any respirator with nuisance level capacity should never be used for potentially high exposures when painting, etc. Always use a catridge in that case. Pancakes fit under the helmet well too. Go to the link below, down load the respirator catalog and look on page 15. Pancakes are P100s with Nuisance level (NL) odor relief. NL means it has a layer of charcoal which absorbs organic vapors. They work well for welding and fit in the North 5500 or 7700 half face respirator.
http://www.northsafety.com/TriggerW...ue&CDTID=a2de4ac6-0971-431d-ac14-d9496fd9b052
If it is in your budget, consider Powered Air Purifying Respirators (PAPR) that attach to welding helmets. Same cartridge selection applies as the filter air and pump clean air into your helmet.
I also like Moldex products. They make numerous filtering facepiece (double strapped NIOSH approved respirator--commonly called dust mask). Not partial to the brands I have mentioned as any brand will work if selected correctly and it fits your face.
I have assessed hundreds of metal exposures(grinding, sanding, foundries, welding, etc.). All types from radiator shops (lead fume), metal fab (e.g. Warn Winches) & pipe welders (mild steel), stainless steel welding (chormium fume), bronze welding at art foundries, etc. Stick welding has produced the highest exposure concentrations in my experience. Wire feed was next and TIG was the least. Generally exposure assessments are conducted over the full days work shift. My guess is most of you weld intermittently and not straight for 8 hours. So relatively your exposures might be below most exposure limits. Respiratory protection is still absolutely recommended. Got to protect those lungs so you can power your creations.
Hope that was helpful and will be flame free knowing you all have torches.
Do I qualify for a free frame from anyone???
urmb