Cooksey, Philip. Recessed Lighting, Insulation, and Fire. The International
Fire Chief. September, 1980.
Abstract: This article explains how the combination of recessed
lighting fixtures and insulation can result in a fire. In 1976, Oklahoma
City experienced an unexplained wave of attic fires. The investigation pointed
to combustible insulation as the cause. The Assistant Fire Chief Darby lead
a further investigation, which discovered that insulation of a fireproof
nature was also involved. Darby investigated common heat sources in attics
and discovered that recessed light fixture standards were not being enforced.
The National Electric Code requires three inches of clearance between thermal
insulation and light fixtures.
Darby conducted tests to prove his theory: insulation covering light
fixtures was trapping heat generated by the fixtures allowing them to ignite
nearby combustibles. The tests proved his hypothesis. An oven effect was
created when insulation was placed too close to lighting fixtures. The heat
produced could not escape and ignited combustible materials.
One method that did maintain safe temperatures was a five-sided metal
box enclosing the light fixture. This box absorbed the heat and allowed
it to spread and dissipate. As a result, Oklahoma City enforced new codes
concerning insulation in newly constructed attics. All recessed light fixtures
must be protected with the five-sided metal box to allow heat to escape.
The code changes have resulted in a large reduction in attic fires in the
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