Chapter 1: Introduction

1。1 Overview 

Live fire training evolutions are a popular training method utilized by many fire departments。 They provide participants with an opportunity to practice firefighting techniques, as well as develop an understanding of the thermal conditions inside structural fires。 

Unfortunately, every year firefighters are injured during training, and occasionally some training incidents are fatal。 The dangers of structural firefighting are well recognized, but the hazards that firefighter trainees and instructors are exposed to in training environments can be significant and may not be appreciated prior to the activity。 Some firefighter injuries in training incidents occur as a result of exposure to dangerous thermal conditions characterized by high temperatures and high heat fluxes。 Severe thermal conditions can be generated in live fire training incidents when: 

1。 Unsafe fuel packages are used 

2。 Inadequate or improper ventilation is provided 

3。 Fuel packages with large heat release rate (HRR) are burned in small rooms, and 

4。 Sequential burn evolutions occur with minimal time between burn evolutions 

NFPA 1403, Standard on Live Fire Training Evolutions, is intended “to provide a process for conducting live fire training evolutions to ensure that they are conducted in safe facilities and that the exposure to health and safety hazards for the fire fighters receiving the training is minimized。”1 As such, in keeping with the intent of NFPA 1403, a fire instructor planning a burn evolution for training purposes should conduct a hazard assessment to consider the thermal conditions which will be generated by the planned event。 Important parameters to be considered in a hazard assessment should include fuel packages, amount of ventilation and room size。 

Fuel packages have a significant impact on the thermal conditions inside a structural fire environment。 NFPA 1403 provides no specific guidance on suitable fuel packages。 NFPA 1403 only states that fuels must be wood products, the amount of fuel must be necessary to create the desired fire size and the fuel load needs to be limited to avoid flashover or backdraft。 The resulting temperatures and heat flux firefighter trainees and instructors are exposed to inside the training environment are influenced directly by the HRR generated by the fuel packages。 The composition and configuration of fuel packages affect the HRR, hence selection of fuel packages is an important step in any hazard assessment。 

The properties of room enclosure materials can also affect temperature development inside a burn room。 Rooms which are well insulated will generally retain heat within the compartment, thereby increasing the severity of thermal conditions experienced as compared to a room that is not well insulated。 

Ventilation during a particular evolution will affect thermal conditions and the position of the smoke layer within burn rooms。 The role of ventilation needs to be accounted for in a proper hazard assessment。 

Room size has an influence on the thermal conditions inside the training structure。 NFPA 1402 does not provide guidance on the proper dimensions of a burn room。2 Therefore, burn room sizes are not uniform and the volume of space in burn rooms varies greatly for each live fire training facility。 For a given fuel package, the severity of thermal conditions is decreased with increasing room size。 Thus, utilizing smaller rooms for burn evolutions has the potential to increase the severity of thermal conditions experienced within the room。 

In addition to the above, often multiple sequential burn evolutions are conducted over the course of a day as part of a training activity。 If a subsequent burn evolution is conducted before allowing the room enclosure to cool, more severe thermal conditions will be produced than if the room is allowed to cool。 As this process is repeated multiple times, the initial ambient temperature inside the facility can become even further elevated to yield an even more severe set of thermal conditions。 The 2012 edition of NFPA 1403 requires the following: