Service Tunnel Ventilation 3

[dik]

I have an electrical service tunnel about 500' long with an 8'x8' cross section. Ozone is not an issue, but Radon might be.

Is there a standard for number of air changes that should be used to determine the fan required? With or without radon?

If radon is present, is there a requirement for treating the 'radon laden' air?

Dik

 

[plasgears]

You may need to work with an air purifying mfr. They may have in mind a counterflow air scrubber to collect and isolate the radon before allowing human entrance to the tunnel. One such mfr is Advanced Air Techn. in Corunna, MI.
advairtech.com

 

[chicopee]

First of all, find out the ozone and other contaminant(H2S,CO,C2H,etc..) concentrations released into the tunnel to determine if you have a problem;, then determine the acceptable concentration of ozone and other contaminants acceptable within the tunnel; then you can base your fan CFM on the rate of contaminant release so that you have acceptable limits of contaminants.

 

[chicopee]

I worked out the math regarding your problem. Assuming constant generation of radon or otjher contaminants, the solution will be an exponential equationuntil steady state is achieved. Upon steady state ventilation equation in the form of mass rates will be:
d(Mal)/dt= d(Mcg)/dt x Mat / Mctf
where
d(Mcg)/dt=mass rate of radon or other contaminants
generated
Mat=mass of air in the tunnel
Mctf= mass of radon or other contaminants
acceptable within tunnel-dont forget factor
of safety when using ACGHI limits
d(Mal)/dt=mass rate of air flow in tunnel

 

[unclesyd]

There was/is an OSHA/ANSI requirement for air changes in a confined space such as you describe. The rules were similar to the "Confined Space" requirements. I think in your case it could even be a "Confined Space".