air

The air around us is a mixture of gases, mainly nitrogen and oxygen, but containing much smaller amounts of water vapor, argon, and carbon dioxide, and very small amounts of other gases. Air also contains suspended dust, spores, and bacteria. Because of the action of wind, the percent composition of air varies only slightly with altitude and location. The table indicates the composition of a typical sample of air after all water vapor and suspended …

…are likely to occur at intermediate pressures. The figure shows how the explosiveness of a hydrogen-oxygen mixture depends on temperature and pressure. Explosion occurs in the shaded area. At 800K and low pressure, no explosion occurs. As the pressure is raised, the mixture enters the chain reaction explosion region. As the pressure is raised further, the mixture is no longer explosive. When the pressure is increased even more, the mixture enters the thermal explosion region.