How to use the confined space oxygen checker
This page checks whether the oxygen reading on the instrument falls inside the range your site works to. Enter the reading together with the lower and upper limits from the standard you apply and its position against those limits appears, with the distance to each one on its own line.
The comparison is plain: below the lower limit, at or above the lower limit and at or below the upper limit, or above the upper limit. Values are rounded to the one decimal place shown on screen before they are compared, so the number and the conclusion never point in opposite directions. Statutory figures were not confirmed in an authoritative source, so none are offered and the limits are yours to enter. Values are as of October 2026.
Toxic gas concentrations, the lower explosive limit of flammable gases, and purge airflow and blower time are not covered. The page does not decide whether entry is allowed, and it does not account for sampling position, differences with depth, or the calibration state of the instrument. Confined space work needs measurement by a qualified person and a permit procedure. This calculator is for reference and does not replace design. Review by a qualified engineer is required.
Frequently asked questions
Statutory figures were not confirmed in an authoritative source, so none are given. Enter the lower and upper limits from the standard your site applies and the reading is compared against those only.
It does not judge entry. It only shows where the reading sits against the limits you entered; actual entry follows measurement by a qualified person and a permit procedure.
Purge airflow and blower time are not covered. This page only checks whether the reading falls inside the range you entered.