Fig 6Testing a tank's air before anyone goes in
04812ft1 O2 %2 LFL %3 H2S ppm12.0 ft0ENTRANTS INENTRY PERMIT

Tap or click a depth, drag, or press the arrow keys to move the probe. Shift plus an arrow steps 4 ft.

1910.146(b) · 12.0 ftSteady
  1. Oxygen1910.146(b), hazardous atmosphere, item (3) 0 %limit 19.5 to 23.5 % Within the limit
  2. Flammable gas1910.146(b), hazardous atmosphere, item (1) 0 % of LFLlimit 10 % of LFL Within the limit
  3. Hydrogen sulfide1910.146(b), item (4), and 1910.1000 Table Z-2 0 ppmceiling 20 ppm Within the limit

Who acts when a condition is not allowed

The three people named in the standard each have a duty. Choose one to light up its equipment in the drawing.

An invented example of one tank whose air changes with depth. The gas profile is not data from a real space. The limits are paragraph (b) of 29 CFR 1910.146 and Table Z-2 of 1910.1000, which also allows a short peak above the 20 ppm ceiling that this figure does not model.

The 4 ft step and the slow needles follow Appendix B, which the standard calls non-mandatory guidance. Examples in the appendixes use other triggers, such as 10 percent or more. This figure uses paragraph (b) only. Illustrative, not compliance advice.