LETHAL R-134a concentrations from evaporator failure

Thomas Perry thomas.perry at dol.net
Mon Nov 3 12:22:14 EST 1997


According to several reliable HVACR magazines this study at WPAFB no one
passed out or died in this study and your chances of dying from exposure to
R-134a is very low. 

ghg at worldserver.com wrote in article <878560704.20754 at dejanews.com>...
> LETHAL R-134a CONCENTRATIONS IN PASSENGER COMPARTMENTS MAY OCCUR
> FROM EVAPORATOR FAILURE
> 
> In August 1997, a study was done at the Armstrong laboratory, Wright
> Patterson Air Force Base, Dayton, OH. The report, "Human Inhalation of
> Halon 1301, HFC-134a and HFC-227ea for Collection of Pharmacokinetic
> Data" was authored by A. Vinegar, R. Cook, J McCafferty, M. Caracci, and
> G. Jepson.
> 
> The concentration of R-134a being used was extremely low and (then
> thought) that nothing bad was going to happen. To quote from the bottom
> of page 10 (page 11 if abstract prepended), "Subject #3 was the first
> volunteer exposed to
> 
> HFC-134a.  The exposure concentration was 4000 ppm (0.4% v/v) and was
> scheduled to last for 30 minutes with a 5 minute postexposure evaluation
> period as was accomplished in the Halon 1301 portion of the study. 
> Approximately 4.5 minutes into the exposure, the subject lost
> consciousness and both pulse and blood pressure dropped to zero."
> 
> The test was aborted and medical personnel intervened and revived the
> subject.
> Suppose it wasnt a test in a medical lab, that person would be "dead".
> 
> The industry, has in general, tried to "coverup" this "problem", often
> reporting "Human Subject Faints During Botched Air Force R-134a
> Inhalation test".  They then go on to theorize that the nurse wiggled the
> blood drawing needle and that made the subject "faint".  See (on the web)
> www.autofrost.com/humanhal2.pdf to download your own copy or call Monroe
> Air Tech at 1-800-424-3836 for a copy. Be your own judge.  Using "0.4%"
> (4000 ppm) parts per million of R-134a vapor in air as the "lethal"
> amount, the following calculations were performed on several late model
> cars.  They assume a bad evaporator leak or rupture, allowing the factory
> listed charge amount
> 
> to escape into the passenger compartment.  R-134a is heavier than air, so
> if the air is not "stirred" by a fan, heavier concentrations will be
> found in low spots and lower in high spots.  For these purposes, we will
> assume the air is stirred and the concentration is uniform.
> 
> The specific Volume of R-134a vapor at "normal" pressure (from the NIST
> Standard Reference Database 23 "NIST THERMODYNAMIC PROPERTIES OF
> REFRIGERANTS AND REFRIGERANT MIXTURES") is 3.69 cubic feet per pound
> (cf/lb).  If you blow off a 1 lb can of R-134a into am empty garbage bag
> (sealed), it will occupy 3.69 cubic feet.
> 
> 	     SPECVOL134a CF   R-134a CHG lb         1        1,000,000 parts
> conc. (ppm) = -----------   X -------------  X   --------  X
> ----------------
> 		  lb                            Int.Vol CF   per million
> 
> 1998 CAR		Interior(CF)	lb R134a  pass.conc ppm  Times
> lethal
> Ford Escort		87		1.75	  74,224	  18.6
> GEO Prism		84		1.7	  74,679	  18.7
> Chevy Cavalier		92		1.5	  60,163	  15.0
> Ford Taurus		101		2.13	  77,819	  19.5
> Ford F150*		80		2.38	  109,778	  27.4
> Toyota Camry		96.8		1.88	  71,665	  17.9
> Ford Mustang		83		2.13	  94,695	  23.7
> Chevy Malibu		98.6		1.75	  65,492	  16.4
> Honda Accord		90.4		1.43	  58,371	  14.6
> Chevy S-10*		80		2	  92,250	  23.1
> Chevy MonteCarlo	96.1		2	  76,795	  19.2
> Olds Cutlass Supreme	95		1.75	  67,974	  17.0
> Buick Skylark		87		2.25	  95,431	  23.9
> BMW 5 Series		93.5		3.27	  129,051	  32.3
> * Estimated, since interior volume was not available
> 
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