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Question:  I was wondering if you might be able to provide some guidance on thermal fogging a 4-story office building.

 The building, located in a large city in the south, is some 160 years old. They sustained smoke damage from a fire in the adjacent building (restaurant kitchen fire). The building has a sprinkler system and monitored fire/smoke detection systems. This will be my first application in a large scale building, and I have some questions about thermal fogging: 

Answer: from SCRT Technical Director, Jeff Bishop

Foremost, recall the principles of deodorization:

  1. remove the odor releasing source, as practical.  In this case, this principle does not apply.
  2. clean all surfaces and materials subjected to significant contamination. 
  3. recreate the conditions of odor penetration with an appropriate odor counteractant.
  4. seal or encapsulate surfaces as required (usually scorched or discolored materials, but only after cleaning). 

Your primary effort in this case would be to thoroughly clean all surfaces subject to contamination (principle #2) using a detergent, deodorant solution.  Done properly, this should physically remove most of the smoke and odor on accessible surfaces.  The rest must be paired or neutralized with fogging operations to “chase” the smoke and odor in cavities into which it may have penetrated. 

  • Do we need to shut off all power to the building before treatment to eliminate the possibility of electrical arcing?

No.  The objective when thermal fogging is to fog until the other side of a room or area becomes obscure, but doesn’t “disappear” entirely.  While secondary combustion is an outside possibility, it is rare.  In fact, I know of only one situation in which it occurred and that was because untrained persons over-fogged a confined area (electrical raceway in a school building flooring system). 

Of course, it would be ideal to have everything in a building shut off, but that probably is impractical and unnecessary, so use your discretion here.  Seldom do we shut off building power when engaging in any deodorization process (certainly ozone is not flammable!).  It is, however, prudent to extinguish pilot lights and flames from gas appliances (e.g., kitchen appliances, water heaters, fire places), but I’ve even missed those on occasions with no adverse effect, when thermal fogging is done properly.    

And remember, fallout from over-fogging (oily residue) is as big a potential problem as secondary combustion.  All the more reason to fog reasonably, leave the building closed and exposed to the deodorant fog for 30 minutes to an hour, air out the building, sniff for residual odor and repeat the procedure as required.  Ultimately, ozone deodorizing may be required in confined pockets of residual odor. 

  • Do we need to disable the fire/smoke detection systems? Or is covering the detectors sufficient?

Since you’re creating smoke, obviously smoke detectors will be set off.  But it really depends on how sensitive the system is.  If the smoke detector is not hard wired and is the stick-up type, you may be able to seal it with a plastic sandwich baggie – or simply take the battery out.  If the system is hardwired and designed to contact the fire department, the system will have to be disabled. 

In any event, it’s usually a good idea to contact the local fire department to let them know that you’re engaging in fogging operations, in case some good citizen sees smoke coming from vents or leaks in the building envelop and calls the fire department.  They still may have to respond, but at least they won’t have to run over anyone on the way if they suspect that it’s fog rather than fire smoke.

  • Do we need to disable the sprinkler system? If so, is that something that must be done by the installer?

Most sprinkler systems are activated by heat rather than smoke.  Regardless, it’s prudent to get the name of the company that installed or services the system and get some information from them.  It’s imperative that no sprinkler system be activated and create water damage.  Obviously!

  • The building will be uninhabited during treatment.

And that’s critical too.  No building should be occupied when deodorant chemicals or gases (i.e., ozone) are being dispersed into airspace. 

  • How far in advance do you typically notify the local fire department? In your experience, has the fire department required a "fire watch" person/s on site during treatment? If so, how many? (1? or 1 per floor?)

When a fire detection or suppression system is temporarily disabled, and especially in an occupied building, OSHA requires that a fire watch be posted for the duration of the disablement.  Not exactly sure what the regulation says, but one person per floor sounds reasonable.  If they are present when the fog is present, naturally they will need full eye, skin and respiratory protection. 

Any other suggestions or comments you may have in order to "do no harm" would be greatly appreciated! 

Hope this helps.  Be sure to use a little common sense as well.

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