d. Working with TLV Data. The following examples will provide practice in
using TLV's and related data.
(1) Example 1. Workers in an industrial shop on an Army installation are
exposed to a perchloroethylene solvent of the following concentrations, for the following
periods: l hour at 50 parts per million (ppm); 2 hours at ll0-ppm; 3 hours at 30-ppm; l l/2
hours at l5-ppm; and l/2 hour at 200-ppm.
(a) Refer to preceding paragraphs and to Appendix E, then answer the
1 What is the TLV for perchloroethylene?
2 What is the TWA exposure for these workers during the 8-hour
3 Are the concentrations to which these workers are exposed
1 By referring to Appendix E, we determine that the TLV for
perchloroethylene is 50-PPM.
2 The TWA exposure is determined by substituting our data in the
(T1 x C1) + (T2 x C2) + (Tn x Cn)
3 Substituting, we have:
TWA = (1 x 50) + (2 x 110) + (3 x 30) + (l.5 x l5) + (0.5 x 200)
1 + 2 + 3 + l.5 + .5
50 + 220 + 90 + 22.5 + 100 = 482.5 ppm = 60.3
4 The TWA exposure is 60.3-ppm.
5 The exposure is out of compliance with the TLV-TWA.