Oxygen Enrichment #
The normal oxygen content in the atmosphere is around 20.95%. If a location has a value which exceeds this, its atmosphere is said to be oxygen enriched.
E.g.: – gas manufacturing plants, hospital operating theatres, & around oxy-acetylene equipment.
Oxygen enrichment has three disadvantages #
1. It can lower the ignition temperature temperature of flammable materials as shown:
| Material | Air | Increased Oxygen |
| Ignition temperature °C | Ignition Temperature °C | |
| Hydrogen Sulphide | 260 | 220 |
| Acetylene | 305 | 296 |
| Ethane | 515 | 506 |
2. Oxygen enrichment significantly raises the upper explosive limit (UEL) of the majority of gases and vapours, thereby widening their flammable range:
| Materials | Air | Increase Oxygen | ||
| LEL% | UEL% | LEL% | UEL% | |
| Methane | 4.4 | 17.0 | 5.2 | 79 |
| Propane | 1.7 | 10.9 | 2.3 | 55 |
| Hydrogen | 4.0 | 77.0 | 4.7 | 94 |
3. It can allow an atmosphere to be ignited with much lower values of electrical energy.
Explosion protected equipment will have been tested in normal atmospheric conditions. Equipment for used in an oxygen enriched atmospheres must be specially tested and certified.
