Hypoxic design oxygen: the fuel's lowest ignition threshold less a 0.75-point margin (EN 16750); ambient air is 20.9%
Ignition threshold minus 0.75 pt O2observed
| Value kind | observed — Reported measurements, counts, and specifications keep the precision and scope stated by their source; an exact specification is not treated as a range. |
|---|---|
| Scope | The design level depends on the protected fuel and arrangement, so there is no single operating range. The 15-17% and 13-15% bands in the literature are personnel-access categories, not design levels. Operating settings also allow for sensor tolerance and control margins. FM Approvals Standard 5800 and FM Property Loss Prevention Data Sheet 4-13 set separate FM requirements. |
| As of | 2020-11 |
| Source | EN 16750:2017+A1:2020, clauses 5.5-5.6 (design concentration = lowest applicable ignition threshold minus 0.75 percentage point O2); Mueller, SUPDET 2017 (method and paper-archive example) · EN 16750 clauses 5.5-5.6, Figure 1 and Table 2; Mueller p.2 design-concentration method |
| Review | checking…review by 2027-06-30 · standard cadence |
| Recorded changes | last 2026-10-15 · 3 revisions tracked |
| Claim id | operating-oxygen-level-for-hypoxic-fire |
Where the guide uses it
← Full numbers register — every date-stamped figure in the guide, with revision history.