Last year I helped to build The Serpent Mother with the Flaming Lotus Girls. I welded and ground a lot of stainless steel sheet. Here is a safety guide I created for safely working with stainless steel.
The vertebrae of Serpent Mother are being made of welded stainless steel. The fumes contain carcinogenic hexavalent chromium, sometimes written as CR(VI).
Respirator Procedures for Welding Stainless Steel
- When you are welding stainless steel, wear a 1/2 facepiece respirator with a filter that has a “100″ rating.
- If you are working within 10 feet of welding, or if you are grinding or sweeping, wear a “95″ rated disposable respirator or 1/2 facepiece respirator.
- The dust is much less toxic than fumes but should be treated with care. Burning and smoking it should be done with caution.
- Recognize that the bother respirators cause is worth it. They keep scratchy throats and lung cancer away. They can be slightly uncomfortable. It is difficult to be heard when speaking through a disposable respirator and you have to really speak up to be heard through a 1/2 facepiece respirator.
- Always work in an area with excellent ventilation. Outside is best. If not possible, open windows & doors, push (or pull) fumes outdoors with a fan or fume extractor.
- Alert people nearby what you are welding and of the danger. If indoors, alert everyone nearby and suggest they wear “95″ rated respirators.
- After being near welding for a long time, be sure to shower when you get home to get the particles off you. Keep your work clothes separate from your other clothes. Do not eat your work clothes.
- Get your own disposable and 1/2 facepiece respirators. They will fit better, you’ll know that they’ve been cared for, and they won’t smell of someone else’s copious sweat and snot.
- When you’re not using them, keep your respirators in a plastic bag. “OV” filters will slowly degrade if left in the open air, decreasing their effectiveness. Also, the plastic bag will keep potentially toxic shop dusts out of the insides.
- Replace the filter in your respirator if you detect a funny taste or smell through it or if it becomes difficult to breathe through. Those are signs that it’s useful life is over. There aren’t any hard and fast rules about this but you should get 10-50 hours of actively breathing through the respirator.
You must use at least an “N95″ or better respirator to protect yourself from stainless steel dust and fumes. It’s a very good idea to use a better respirator because the better fit and filtering will ensure safer working, especially for people that are less experienced (like myself!) with such work environments. The literature from 3M and OSHA says that a 95 rated respirator is enough to protect you from the dangerous levels of chromium IV CR(VI) in stainless steel dust. And finally, scientists simply haven’t figured out exactly why people in the welding professions have higher lung cancer rates.
Upside of a 1/2 faceplate respirator compared to disposable
- They fit better
- They can be bought sized to your head. If you have a small head, 3M’s 7500 (silicon) and 6000 (rubber) series respirators come in different sizes (7501-small 7502-medium 7503-large. 6100-small 6200-medium 6300-large)
- The highest rating is 100 (also called “HEPA”).
- They can accept several different filters for different protection needs.
- It’s easier to get it to not fog up your glasses than disposables.
Downside of a 1/2 faceplace respirator compared to disposable
- It’s slightly harder to breathe through them than disposable respirators
- It’s harder for others to hear you speaking through them.
- 100 rated filters are a little harder to breathe through than 95 rated filters.
- They are more bulky than disposables, taking more space in your bag and on your face.
- The respirator costs $10-20. But the filters cost a little less than disposables so you’ll save money in the long run.
Downside of a disposable respirator
- An imperfect fit can go unnoticed
- They don’t look as cool
- They don’t have cute PINK filters on them!
- rated for nuisance level organic vapors is better for keeping bad organic fumes away but doesn’t help for stainless steel.
For disposable respirators, 3M suggests their 8214 or 8514 for use with stainless steel. These are N95 and cost about $3 each. If you want to get an N100 disposable, the 3M brand model 8233 is the thing. Or for a P100, the 3M brand model 8293. They cost about $7 apiece.
For higher quality respirators, 3M suggests their “6000 series” or “7500 series” half faceplate respirators fitted with their 2091 or 7093 filter. These are P100 filters, the whole thing costs $15-30 but lasts a bit longer and is safer.
One good source to buy them is Praxair, 1690 Evans Avenue San Francisco, CA 94124 — our local welding store. They are very helpful and will let you try them on.
The Long Answer
The worisome byproduct of stainless steel welding is hexavalent chromium, also refered to as Cr(VI). It’s the same stuff from the movie Erin Brockovich. Though as to not frighten one too much, the people of Hinkley, CA were drinking water that had 1,000 times the legal limit of chromium for 20 years before bad things happened. And (from http://www.dhs.ca.gov/ohb/HESIS/cr6.htm#SPECIAL_CONTROL)
The best estimate of the excess risk of lung cancer from exposure to hexavalent chromium compounds at California’s current Permissible Exposure Limit (PEL), every working day for 40 years, is 8 cases of cancer in every 100 workers exposed
Studies have suggested that all people in the welding profession are at higher risk for cancer. There are many unknowns about the increased risks even after all the studies. Many important questions are not fully answered. Questions like: exactly what particles are bad for you, and what is the best way to protect ones self.
CR(VI) guide: http://solutions.3m.com/wps/portal/3M/en_US/Occupational-Health/Environmental-Safety/Whats-New/Hexavalent-Chromium/ (then click on “Frequenly Asked Questions and Answers Regarding the Hexavalent Chromium Cr(VI) Standard”
Here’s a really long report about hexavalant chromium. I snipped bits below and wrote what I think it means to us. http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=FEDERAL_REGISTER&p_id=18599
3. Dermal Absorption of Cr(VI) Both human and animal studies demonstrate that Cr(VI) compounds are absorbed after dermal exposure.
Wear gloves when handling stainless steel grinding dust and welding leavings. Take a shower after being in the shop when there’s stainless steel welding.
About 10 times more chromium penetrated when potassium dichromate was applied in petrolatum than when applied in water
If you get lubricating oil et all and stainless steel dust on your skin, you should wash it off quickly.
The estimated half-life for whole body chromium retention is 22 days for Cr(VI) (Ex. 19-1). The half-life of chromium in the human lung is 616 days
It sticks in your lungs. Don’t breathe it!
OSHA does not believe that a specific requirement mandating use of HEPA filters for air purifying respirators used for protection from Cr(VI) is justified, and has not included such a requirement in the final rule. For air-purifying respirators, in addition to the option of providing a respirator equipped with a filter certified by NIOSH under 30 CFR Part 11 as a HEPA filter, the Respiratory Protection standard allows employers several alternatives. Under 1910.134 the employer may also provide either (1) An air-purifying respirator equipped with a filter certified for particulates by NIOSH under 42 CFR Part 84; or (2) an air-purifying respirator equipped with any filter certified for particulates by NIOSH where dealing with contaminants consisting primarily of particles with mass median aerodynamic diameters (MMAD) of at least 2 micrometers. OSHA believes these requirements are appropriate for protection from exposures to Cr(VI).
A type 95 is 95% efficient while a type 99 is 99% efficient and the type 100 is the most efficient and equivalent to the old HEPA filter.
GMAW tends to produce lower [chromium] exposures than SMAW
- -) We’re using GMAW (otherwise called MIG welding)
LEGAL EXPOSURE LIMITS Cal/OSHA’s current Permissible Exposure Limit (PEL) for water-soluble and certain water-insoluble hexavalent chromium compounds is 0.05 milligrams of chromium per cubic meter of air (0.05 mg/m3). The PEL for zinc chromate is 0.01 mg/m3. The PEL for chromyl chloride is 0.15 mg/m3. Legally, exposure may be above the PEL at times, but only if it is below the PEL at other times, so that the average exposure for any 8-hour workshift is no greater than the PEL. Measuring the amount of hexavalent chromium in the air is the only reliable way to determine the exposure level. The current Permissible Exposure Limit does not adequately protect against lung cancer. We recommend that the amount of hexavalent chromium in the air a worker breathes be kept as low as possible.
No, I don’t know how much chromium is put into the air by, for example, 1 welder. I wish I did. Anyone???
http://www.3m.com/intl/CA/english/market/traffic/ohes/ They have a “respiratory selection tools” program at the bottom of the page.
Article from the ‘nickle institute’ http://www.nickelinstitute.org/index.cfm/ci_id/229.htm
Highlights: Low fumes is good. TIG is really good for that. MIG creates much less CR(VI) than stick welding
This possibility has been explored in a number of epidemiological studies of welders, categorized according to the materials with which they worked and typically extending over periods of more than 20 years since first exposure. The most extensive of these was the IARC study, which pooled data for more than 11,000 welders in nine European countries, separating data for shipyard welders, mild steel welders and stainless steel welders. Overall there was an excess mortality from lung cancer but this could not be related to duration of employment or cumulative exposure to total fume, total chromium, hexavalent chromium or nickel. As a result, IARC classified welding fume in Group 2B, that is possibly carcinogenic to humans.
Mild Vs Stainless Steel Welding
In a number of other, national, studies, stainless steel welders have been compared with mild steel welders or a control group of non-welders. It has not been possible to show a consistent pattern of excess lung cancers attributable to stainless steel fume from these studies. Indeed there have been indications that the incidence of lung cancer is less among stainless steel welders than in mild steel welders. It has been speculated that stainless steel welders are more highly qualified and remunerated and therefore generally healthier than their mild steel welder counterparts. However, there remains the slight excess of lung cancers which has been found for welders as a whole, for which no fully satisfactory explanation has been advanced.
Reference 1. How effective are the Part 84 filter respirators against particles smaller than 0.3 micrometer in diameter?
(note that welding hexavalant chromium particles are about 0.2 micrometers)
The 0.3-micrometer diameter used in the certification testing is approximately the most penetrating particle size for particulate filters. Although it seems contrary to expectation, smaller particles do not penetrate as readily as 0.3-micrometer particles. Therefore, these respirators will filter all other particle sizes at least as well as the certified efficiency level.
Sean at Praxair says about welding stainless:
- Use 3M 2097 with charcoal filter. That’s a P100 with Nuisance Level Organic Vapor Relief and Ozone Protection. Fits 3M 6000 Series Facepiece with Bayonet Attachments
- “Welding outside is always better. If indoors, be sure to keep the windows and doors open and use an exhaust system”
- When the filters start to smell bad, change them. Something like 16 hours of usage.
Bebe from Airgas says
- Airgas (Pat is the head salesman) open 7:30-5pm
- the only reason to get a 1/2 facepiece mask is more durable & last longer than disposable mask.
- Bebe said that the 3M rep said “when you smell or taste something odd, change it.”
- filters last “3-6 hours”
- Get a fume extractor! The fume extractor has to be just a few feet over the work area.
- People working within within 5-10 feet of the work should wear a mask.
- Respirators rarely come sized for different heads. It’s not needed.
- Their sister company, “ready arc” 510-527-4080 can rent a fume extrator. We might think about buying a fume extractor. $500-1000 new, it sucks air in and filters it. Feh, use a fan…
(I haven’t read and summarized the following articles yet)
http://www.osha.gov/SLTC/healthguidelines/weldingfumes/recognition.html I can have a look in more detail when I get back from the playa (yay), but seems to have a lot of useful info.
It is a bit difficult to get some of the other meta-analyses and reviews cause a lot of them are old (online journals have only been fancy since about 97ish) and not carried by the UCSF library.
A journal article the boys might not want to see: The risk of male subfecundity attributable to welding of metals. Studies of semen quality, infertility, fertility, adverse pregnancy outcome and childhood malignancy
Some interesting results, with possibly radient heat being more trouble than the metal itself!
I have tried to find some reference to particulate size of stainless et welding but no luck yet. However this is another MSDS with permissible exposure limits – perhaps we could use this in choosing our equipment?: http://www.bocgases.ca/newsite_eng/images/msds_nat_stand/958_eng_stainless.pdf
What are the different types of filters? N, R, and P. 95, 99, and 100. OV
N – not rated for their being oil in the air. If there is oil, the filter will lose its effectiveness quickly.
R – resistant to oil being in the air. Can be used for 1 day where there is oil and then must be discarded.
P – proof against oil being in the air.
95 – filters 95% of particles of 0.3 microns (and it does at least as well for particles larger or smaller)
99 – filters 99% of particles
100 – filters 99.97% of particles
OV – Organic vapors are filtered out to at least some extent. Most are rated for “nuisance OV” which doesn’t make otherwise dangerous vapors safe but is still helpful against scratchy throats, coughs and the like.