Values of CO and soot yield

[Bojan]

Hello!

What I so far understood is that both values change with time, since the burning is being affected by ventilation. However, some values should be implemented in FDS nevertheless. I looked up in NFPA Handbook for some values, and I found interesting work at http://www.branz.co.nz/cms_show_download.php?id=6502dc9e0bcd36a863218fc6039fef7e1a2b13f8

In the book, the values of soot yield of 0.1 and CO yield of 0.02 is recommended. The second source recommends soot yield of 0.07 kg/kg. I have fire in an atrium and it is fuel controlled all the time. The fuel is upholster furniture (polyurethane foam) and some electric equipment located in the corner of atrium as well.

Another question is about measurement of CO. If I understand correctly, when I implement CO measurement point somewhere in space, I will get mass fraction of CO in the air (kg/kg). How this value can be used to determine the tenability condition, e.g. compared with the maximum CO levels which human body can stand (obtain from the experiments with animals and from investigation reports)?

[dr_jfloyd]

I would caution against being overly specific in what the fuel in your atrium is.  Today it might be a some upholstered furniture and electrical equipment, two years from today there could be a retail kiosk placed in the atrium, and who knows what could be there in 20 or 30 yrs. The atrium fire protection design must still be adequate.

There are multiple sources of information on no-harm CO exposures. You should first look to any applicable regulations for the location of the atrium to see how (if at all) CO exposure is regulated. Some sources for discussions on CO exposure include NFPA 130; regulations and guidance from US NIOSH, US FHWA , and US EPA; and international entities such as the World Health Organization.

[Bojan]

I agree with you on that, but the purpose of the simulation is investigation of fire incident. So, I can say that I am pretty sure what kind of fuel was there, and that ventilation was not a problem.

The concentrations of CO which can harm people I already found. However, I did not understand how should I compare it with the results from FDS. When I put measurement point for CO, I get output value in terms of kg CO/kg gas. I convert this in percentage, and for example I got 0,25 % CO in air. According to Purser and McCallister in SFPE Hanbook, incapacitation with this percentage of CO in air happens after 10 minutes (when victim is walking). Using Coburn-Forster-Kane or Stewart equation in SFPE Handbook it is possible to calculate percentage of COHb (total hemoglobin in the form of carbonxyhemoglobin) over the time. From this, it would be possible to see if victim could survive, e.g. victims with more than 50% COHb are not likely to survive. Correct me if my thinking is wrong.

[dr_jfloyd]

Your approach of taking the FDS CO predictions and using them as inputs to one of the methods in Purser's SFPE Handbook chapter is fine. Note that FDS also has an FED device (see the FED example in the User's Guide).

[Bojan]

Could you please tell we on which page I can find the example? Everything I found about FED is in Section 16.10.9 but there is no example on how to use the point measurement. Thanks.

[dr_jfloyd]

See the Verification Guide.