Safety Tidbit 4.10
– Air Quality
What happens if you
spill a container of paint stripper with xylene that you bought at Lowes or
Home Depot? Alternatively, you applied the paint stripper on your kitchen
cabinets that you are refinishing. Let’s do a little “back of the envelope”
calculations. Scenario: Determine the final air concentration in ppm in
a 18 ft x 25 ft x 9 ft space, say something like your garage . And say the space
(garage) nominally has five air changes
per hour (your garage door is open). Assume after 30 minutes, 1-liter or about
a quarter of your 1-gallon container of paint stripper spills and evaporates
(or, you applied the stripper to your kitchen cabinets). After all, the manufacturer
says it evaporates quickly and to use it in a well-ventilated area or outdoors.
We’ll assume that all of the stripper
evaporates and diffuses rapidly within the space. However, in practice there
will be areas of high concentration and areas of low concentrations based the
configuration of the space. Now let’s go through the steps:
·
Determine the room volume in cubic feet
(V). Answer - 4.050 ft3 or 114.696 m3
·
Convert the volume of xylene spilled into
mass using specific gravity. Answer - 880 grams
·
Determine how many mg/m3 of xylene are in
the air (Ci). Answer - 7,672 mg/m3
·
Next, using the Ideal Gas Law and the
molecular weight, convert mg/m3 to ppm. Answer - 1770 ppm.
·
Calculate the air flow (Q), given 5 air
changes per hour. Answer - 337.5 cfm.
·
Rearrange the steady-state formula and calculate
the air concentration (C) after 30 minutes
Steady-state formula =
or C=Ci*〖0.5〗^((T/0.693)*(Q/Vr) )
Answer:
145 ppm
OSHA PEL = 100 ppm
I think a respirator may be in
order or better yet engineer out the problem and get a good fan and get more dilution ventilation.
Hope this was helpful and thank you
for reading my Safety Tidbits! Comments and questions are always welcome. ~
Bryan
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