CHST question for October 21, 2026
The CHST question of the day for Wednesday, October 21, 2026, on construction safety math: noise and excavation slopes. Pick an answer to see the explanation and its source.
CHST Domain 1: Hazard and Risk Identification and Control
A sawmill operator works an 8-hour shift: 4 hours at 92 dBA near the sorting line, 2 hours at 105 dBA at the debarker, and 2 hours at 95 dBA at the planer. Use D = 100 × (C1/T1 + C2/T2 + …), where C is the hours at each level and T is the reference duration for level L from OSHA Table G-16a (for example 8 h at 90 dBA, 7.0 h at 91, 6.1 h at 92, 4 h at 95, 2 h at 100). Using OSHA's noise dose method (Table G-16a reference durations), what is the operator's daily noise dose?
Show answer and source: 29 CFR 1910.95, Appendix A
Answer: C. 315.6%
D = 100 x (C1/T1 + C2/T2 + ...), where C is the hours spent at each noise level and T is the reference duration from Table G-16a. For the sawmill operator: D = 100 x (4/6.1 + 2/1 + 2/4) = 315.6%.
On the job
A safety coordinator at a furniture plant studied one finisher's shift: 2 hours at 90 dBA in the spray booth, 4 hours at 85 dBA at the assembly bench, and 2 hours at 100 dBA at the sanding station. Each period's hours were divided by its Table G-16a reference duration and the fractions summed. Because the sanding station used up dose fastest, the coordinator prioritized controls there and checked the total against the action level for the hearing conservation program.
Study aid, not site-specific safety advice. The official rule controls.
Answer C comes from
29 CFR 1910.95, Appendix A(opens ecfr.gov in a new tab)“When the workshift noise exposure is composed of two or more periods of noise at different levels, the total noise dose over the work day is given by: D = 100(C1 / T1 + C2 / T2 + Cn / Tn), where Cn indicates the total time of exposure at a specific noise level, and Tn indicates the reference duration for that level as given by Table G-16a.”
Where it appears on the exam
CHST: CHST5 Domain 1, Hazard and Risk Identification and Control
Practice: Construction Safety Math: Noise and Excavation Slopes
Related reference
Formulas: Noise dose, Noise TWA from dose, Reference duration for a sound level, Excavation sloping (simple slope, 20 ft or less)
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