I was conducting a mock survey at a hospital and during the building tour I came to their maintenance shop. They had a spray paint booth and in the booth was a sprinkler head. Over the sprinkler head was what looked like a plastic bag. I said you can’t cover up the sprinkler heads with plastic bags like that, even in a spray booth. The hospital facility manager told me he received permission from their state agency that it was permissible to cover the sprinkler heads to keep paint overspray from covering the heads.
I knew the state agency people so I called them and asked if they in fact said that. It turns out they did, and they referenced NFPA 25 (1998 edition) section 2-4.1.5, which says:
“Sprinklers protecting spray coating areas shall be protected against overspray residue. Sprinklers subject to overspray accumulation shall be protected using plastic bags having a maximum thickness of 0.003 inches (0.076 mm) or shall be protected with small paper bags. Coverings shall be replaced when deposits or residue accumulate.”
Hmm… That just didn’t seem right to me. Plastic bags wrapped around the sprinkler heads? I understand that you do not want paint overspray on the sprinkler head, but plastic? NFPA 25 says you cannot have any foreign material on sprinkler heads, and now the same standard says you can in spray booths? Well, I had to let it go since the NFPA standard permits it.
Fast forward to the 2011 edition of NFPA 25. The technical committee at NFPA addressed this issue and they changed the standard… a little. Now, section 184.108.40.206.1 says sprinklers subject to overspray accumulations shall be protected using cellophane bags having a thickness of 0.003 inches or less, or thin paper bags. Now NFPA 25 no longer says plastic bags, but says cellophane bags or thin paper bags must be used when protecting sprinklers from overspray. According to the commentary in the NFPA 25 handbook, here is the reason why:
“Testing has shown that lightweight cellophane or paper bags will not adversely affect the operation of the sprinkler. Sprinklers protected by the lightweight cellophane or paper bags may require more frequent inspection than the annual inspection outlined in 220.127.116.11.2 to prevent excessive buildup on the bags. Depending on the use of the spray coating area, the inspection and subsequent replacement of the bags may need to be done daily. In prior editions, NFPA 25 allowed the use of a plastic bag, but this was changed due to concerns about the potential for a plastic bag to shrink prior to sprinkler activation and disrupt the discharge pattern.”
So… My suspicions were partly justified. A plastic bag on a sprinkler head would melt and disrupt the spray pattern of the sprinkler. I thought it could delay the sprinkler head from operating, especially if it coated the thermal sensing bulb (or solder) and act as an insulator. Anyway, once the new 2012 LSC is adopted, then it will reference the 2011 edition of NFPA 25, and the covers to protect the sprinklers from overspray due to a spray paint booth must be cellophane or paper. And, they need to be changed frequently, perhaps as much as daily, depending on the use of the spray booth.
Today, I would just recommend the hospital remove the spray booth all-together, from their building. It doesn’t seem that the risk of failure to change out the bags once they are accumulated with paint, is worth the advantage of having a spray paint booth.