Problem #1 Same chemical with multiple exposures in an 8 hour period

Chemical G - PEL = 400 PPM

Time of Exposure in hours (t)	Concentration in PPM (x)
1	520
2	480
3	100
1.5	200
0.5	300

Find TWA. Does worker require PPE?

Problem #2 Multiple chemical exposure in an 8 hour period

Chemical	Exposure (PPM)	PEL (PPM)
M	350	300
N	300	350
O	350	400
P	300	250
Q	250	200
R	250	300

Find TLV. Does worker require PPE?