Time weighted average calculations apportion a measured exposure to the interval of time during which the exposure occurred. A worker may have an elevated exposure during one-time interval and a lower exposure in the next time interval. The purpose of time weighting the average is to give a more representative measure of exposure then just a simple mathematical average. (Calculation Methods - Dinardi p.179)
| Variable | Unit |
|---|---|
| Ca | ppm, or mg/m3, or ug/m3 |
| Cb | ppm, or mg/m3, or ug/m3 (as long as every entry is consistent) |
| Tn | minutes |