Check out this interview with brilliant scientist Brett Singer (seriously, he's a genius) from Lawrence Berkeley National Laboratory on our misconception about worst case CAZ Depressurization testing.

Tags: bpi, brett, case, caz, podcast, singer, testing, worst

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Even when gas stoves DO have exhaust fans they capture a small % of the combustion products. Note when a boiling pot is on the outside burners, most of the steam bypasses the exhaust hood. Inside burners get more of the exhaust. Even with 250 CFM the face velocity is way to small to capture all that much. 

solution - stoves need to be enclosed on three sides. NO one makes a stove like this but they should. This will more than double the face velocity an improve capture. Stainless side panels would do it and also eliminate splattering on adjacent counter tops. 

Good point. Now, assuming all of us here agreed, whom do you think we will win over first:
Appliance manufacturers or my wife?

Decades of experience in the Culinary realm give me a slightly different perspective.  It is the capture area of the hood that is of significance.  Installing sides will never go over, but if the hood were required to extend some predetermined amount beyond the cook surface and coupled with an appropriately sized fan motor, I believe the dynamics would fall into an acceptable range.

Hi Jim, just to add to your example from another perspective, a capture hood should also be more than a flat surface with an exhaust hole in the middle and skirting around it.  Take for example the fireplace industry that has to produce a draft without the fan.  By tapering the combustion chamber up to the flue there is a gradual acceleration of the air flow and less turbulence.  I suspect a little more air flow engineering as opposed to aesthetics would add to the effectiveness of hood design.

We must remember that the fan is not pulling the air from above the cooking surface up into the exhaust, just creating a low pressure zone in the vent so that the surrounding higher pressure can push all of that air into the little hole (just like a fireplace).


Actually engineering the flow would make sense. Maybe they need to attach the hood to the pot lid; now there is totally new paradigm.  Air jets blowing upwards around the edge of the cooktop would help also. After all that, there is still a need for some reasonable velocity to contain the products of combustion on the gas stove, the steam and smoke.  Apart from adding more flow, we haven't progressed at all in kitchen exhaust. 

Lizzy bought one of those NuWave induction stoves.  I've always hated electric and loved gas.  

I guess I have bias against induction that I wasn't aware of because even though there are all types of reviews raving about induction, experiencing it in person left me shocked.  (And I try to be open to having my schemas disrupted!)

In my mind cooking with gas is done.  If you haven't tried induction cooking, try it.  If you have tried it, and see any reasonable argument FOR gas, I'd be interested to hear it. 

Very interesting. Brett did a good job of explaining complicated subject and boiling down (pun intended)  points.

my favorite was "If you are going to do test that is going predict an unlikely event will happen then you need to do allot of monitoring to see if this event will happen"

I do not think we will see any changes anytime soon for CAZ but the podcast was a good refresher on the dangers of the gas stove top that I can take forward. I am glad that cfm in still equals cfm out

It also brings forward to me the need for mechanical ventilation. Many problems can be eliminated through dilution.  A good balanced ventilation system designed for the applicable climate is still one of the best things we can recommend for any home.

Good stuff



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