1. Incipient or Beginning phase - Oxygen plentiful, temperature has not built up, thermal updraft rises, breathing not difficult, fire extinguishments by direct application of water at base
2. Growth stage - Fire load and oxygen used as fuel, potential for flashover
3. Fully Developed or Free burning phase - Fire has involved more fuel, oxygen supply depleted, breathing difficult, fire extinguishments reaching major involvement area
4. Decay or Smoldering phase - Oxygen supply not equal to demands, temperature throughout building very high, normal breathing not possible, potential for backdraft