Kitchen hood light test

[ron]

Does anyone have the correct method of how this test is to be performed on welded stainless steel commericial hoods ?

 

[Bryan Holland]

Yes, see section 506.3.2.5 of the 2009 IMC.

 

[Glennman CBO]

Just go by what the code says. As far as actual field inspection, I have them lower the light from the top, or up from the bottom, or whatever works for the installation. Get up close and look for pin holes, cracks/gaps in the welds. You need to be very thorough. I've seen pin holes that were only visible from a certain angle, that cannot otherwise be seen. In other words, just because the light is inside the duct doesn't mean you will instantly see all holes. It helps to turn off the lights in the room where the duct is located.

There was a job at a vocational school once where there were (6) hoods with their individual ducts. There were alot of horizontal runs. We performed light tests on all the sections we could before the sections were installed. Then we inserted the light into the cleanout openings to inspect the joints where they welded the assemblies together. Found several places to fix that would not have been visible without the light.

Use a 100 watt bulb with the drop light guard removed. Works quite well.

 

[Bryan Holland]

To add to Glennman above, we have in some cases scheduled "before hours" light test inspections for larger / more complicated systems. The light test works much better when done before the Sun comes up... (Plus, I got to go home real early that day!)

 

[peach]

pressure is better than light. The contractor will bring out a machine (grease ducts get 0 leakage).. This is one of very few required tests that the code official needs to actually witness. Light is ok if it's only penetrating one or two floors.. more than that, it's hard to verify other than requiring a pressure test.

 

[cda]

Peach do you have code reference for the pressure test?? thanks

 

[hlfireinspector]

We still stand on smoke test. Seal the ends and drop the smoke bomb. It will tell the story every time.

 

[Glennman CBO]

I could see a smoke test or a pressure test as an acceptable alternative method, but the light test is actually the prescribed method in the code. Although, it does state in the '06 IMC section 506.3.3.1 "or an approved equivilent test method". I believe pressure or smoke would be equivalent.

 

[Glennman CBO]

I just noticed in the '09, it doesn't state "or an approved alternative". Only the light test is prescribed.

 

[Bryan Holland]

We will perform a smoke test at final, usually in conjunction with the fire inspectors shut-down and ansul system test. We follow 507.16 of the IMC. (Florida version)

 

[Dr. J]

The duct pressure test is not capable of measuring the very low flow that would result from a few pinholes. The magnahelic gauge readting DP across the orifice plate may say zero, but that is simply because it is not precise enough to read that low. Think about it, the kind of pinhole leak that could slowly ooze grease over the course of months/years may leak, what, a 10th of a cubic foot of air per minute during a test. How do you measure that with an orifice plate? You would need an orifice the size of the pinhole.

I can see the smoke test working acceptably, it is analagous to a soap test on pipe.

 

[peach]

Require a digital gauge.. it's precise enough.

Light test is best until you get above 3 stories.