Appendix E Calculating Non-Standard Shift and Sequential Sample 8-Hour TWAs

DOE-STD-1187-2005

Appendix E Calculating Non-Standard Shift and Sequential Sample 8-Hour TWAs

TWAs based on other time periods, e.g., 6 or 10-hour TWAs, must be recalculated as the

8-hour TWA.

When the 8-hour TWA is calculated from sequential samples in the same work shift, each

sample receives a separate record and the calculated 8-hour TWA is recorded next to

each actual value used to calculate that 8-hour TWA.

When calculating an 8-hour TWA from sequential samples in the same work shift that are

a mix of results that are greater than and less than the LOQ, substitute the LOQ for values

less than the LOQ. The calculated 8-hour TWA will be above the LOQ. For example,

with two results above the LOQ and one less than the LOQ:

(Value1 x TimeV1) + (Value2 x TimeV2) + (LOQ1 x TimeLOQ1) = 8-hour TWA

480 minutes

For example, assume a worker's exposure was unmeasured for 15 minutes at the

beginning of the shift while donning clean work clothing and for 30 minutes at the end of

a shift while showering and donning street clothes. Also assume that the worker was

monitored for a 225 minute period with a result of 0.1 g/m3 and for a 210 minute period

with a result of less than the LOQ of 0.03 g/m3. If the unmeasured periods are judged to

have no potential for beryllium exposure, the 8-hour TWA would be:

(0.1 x 225) + (0.03 x 210) = 0.06 g/m3

480