We had a guy that blew powder, from Walla Walla. He blew the powder on, then next trip scrapped some off, then blew more powder. One place I have done for 10 years still has powder residue in the duct.
Problems
1. New powder stuck to the old powder/grease mixture
2. the fans were not cleaned and sometimes would go out of balance.
3. The fans, especially squirrel fans would be occluded w/the powder/grease and air flow would be seriously affected
4. When cleaned w/a pressure washer, the powder would be blown out of the hood and into the resturant, even with the fan on.
5. This crap would not remove the grease, just cover it up. Fire safety was not improved by powder, but was even more compromised.
6. The fire suppression system was rendered ineffective because the stuff got in the conduit so the detection system did not trip. The nozzles were plugged and the nozzles caps were glued in place.
Advantages
1. Cheap
2. No tool or supply investment required
3. Cheap
4. No need to go on the roof
5. Cheap
This sleaze ball quoted a section of NFPA 96 that I never could find. He left an inpressive certificate that listed a disclaimer. His work was certified for 3 months. No insurance, no numbers on his invoices, prefered cash, no checks. He would look his customer in the face and tell them that the powder was a fire retardant or a sapoanification agent that turned the grease into soap, so the duct system was self cleaning. Some of the customers thought he was great. After he went out of business, some of those customers went for several years w/o any cleaning. Of course, the fire retardent/saponification just kept soaking up hte grease, until it fell from the duct wall.
