OSHA has clearly established that hotwork can not take place in the presence of combustible dusts. 1910.252(a)(2)(vi) Prohibited areas. Cutting or welding shall not be permitted in the following situations:
1910.252(a)(2)(vi)(A) In areas not authorized by management.
1910.252(a)(2)(vi)(B) In sprinklered buildings while such protection is impaired.
1910.252(a)(2)(vi)(C) In the presence of explosive atmospheres (mixtures of flammable gases, vapors, liquids, or dusts with air), or explosive atmospheres that may develop inside uncleaned or improperly prepared tanks or equipment which have previously contained such materials, or that may develop in areas with an accumulation of combustible dusts.
The area of concern that I wish to bring to light is doing hotwork in areas where the combustible dust is either a ways below you or above you. If you are in a large industrial complex that spans many floors, and lets say you are working on the first floor. The area is a combustible dust area, even rated as a Class 2 Div 2 HAZLOC. Your housekeeping program does a good job of cleaning at ground level, but not such a good job on those areas not accessible from the ground. Some of those beams can have 1″ layer of combustible dust on them and span 35′ across with four beams per floor and 10 floors above you.
Do we make any attempt to clean this dusts?
How high do we clean so as to remove the threat of the dust falling on the hotwork?
The other concern is the most common and it is when workers are doing hotwork from a telescopic boom manlift. The permit area is treated as the ground level within 35′ of the base of the manlift (1st mistake). Then the workers go up and out, well outside the 35′ permitted area; keeping in mind that the prep work done for the permit was done SOLELY on the ground level. Now we have workers who are 40′ in the air and for the 40′ below them, each beam is layered in combustible dust. Of course they have a fire watch….on the ground level!
In reality, and yes it is a LOT of WORK, the entire area below any elevated hotwork MUST BE cleaned of any combustible dusts – covering it is NOT a compliance option as I pointed out in my first post. I know everyone has their own standards as to what the word “clean” actually means, but any visible layers of dust should be removed. This dust does NOT have to become airborne to be a hazard. A spark falling onto the layer can cause ignition and a significant and fast moving fire, well beyond what a firewatch should be expected to handle.
The tricky one is when we are welding on the first floor and above us is 8 floors of rafters, support beams, stairs, etc. All kinds of hard to reach places that just do not get cleaned as often as they should because they are so hard and dangerous to access. So…
How high do we clean?
Is it based on dust load?
Do we just clean a 35′ sphere, knowing that the hazard beyond that 35′ mark above us is considerable?
Do we do the same level of prep for a five minute job vs. a two week turnaround/outage where we would have multiple welders doing hotwork 24 hours a day for two weeks?
I would be THANKFUL for all your thoughts on what you think should be done and how you would do the prep for the dust above you. Granting that in the scenario of elevated hotwork, we have no option but to clean all the surfaces below us.