Ignition energy forced

ASTM D 3675 Surface Flammability of Flexible Cellular Materials Using a Radiant Heat Energy Source This method may be used on cellular elastomeric materials such as flexible polyurethane foam and neoprene foam. It employs a radiant panel heat source consisting of a 300 by 460-nun (12 by 18 in.) panel in front of which an inclined 150 by 460-m (6 by 18 in.) specimen of the material is placed. The orientation of the specimen is such that ignition is forced near its upper edge, and the flame front progresses downward. Factors derived from the rate of progress of the flame front and heat liberated by the material under test are combined to provide a flame spread index. The method was developed to test cellular elastomeric materials which could not be tested by ASTM E 162. 

Fireball A burning fuel-air cloud whose energy is emitted primarily in the form of radiant heat. The inner core of the cloud consists almost completely of fuel, whereas the outer layer (where ignition first occurs) consists of a flammable fuel-air mixture. As the buoyancy forces of hot gases increase, the burning cloud tends to rise, expand, and assume a spherical shape. 

---