Regulatory and Environmental Consulting
SPONTANEOUS COMBUSTION IN LAUNDRIES
hundreds of fires occur in laundries, some of which were found to have started
in dryers, under counters or in laundry carts. These fires often occur during the night, hours after the last
employee has left the premises. They can occur anywhere from coin laundries
to tunnel finishers. This article looks at the chemistry and physics of
spontaneous combustion and how to prevent fires in laundries.
How flammable is flammable
Materials which can catch fire and burn are classified as either flammable or combustible, depending on the temperature at which they ignite. When dealing with liquids, this temperature is referred to as the flash point. The lower the flash point, the higher is the degree of flammability. For example, liquids which ignite at temperatures below 38 oC, are considered to be flammable whereas those which catch fire and burn at temperatures above 38oC are combustible. For solids, such as cotton towels, rags or lint, the ignition point is referred to as the critical surface temperature.
Cotton, which is combustible, starts to decompose when the surface temperature reaches approximately 95oC and in the process, generates its own heat. This decaying process is accelerated when the fabric is tightly folded and placed in a confined area. Because it is hot, moist, and has no possible way to dissipate its heat, the oxidation continues to build upon itself, until the garment reaches the critical surface temperature and bursts into flames.
The Fire Triangle
Generally, there are three requirements necessary to support combustion as shown in the diagram:
In a dryer, the fuel can be garments, or more likely lint, which is easier to ignite. The oxidizing agent is oxygen, which is present in air, so where does the heating source come from, hours after the dryer is turned off? To better understand the process we have understand what is meant by oxidation.
So what is spontaneous
Spontaneous combustion is the occurrence of fire without application of an apparent heat source. In a hot dryer, oxidation of fabrics occurs more rapidly than at ambient temperatures. As oxidation proceeds, heat accumulates on the garments, faster than it can be dissipated. The net accumulation of heat continues until the critical surface temperature is reached. At this point the garments are ignited and burn.
1. Never allow large loads to remain
in dryers after the drying cycle ends.
2. Clean the lint screen after every load.
3. Never allow large loads to remain in dryers after the drying cycle ends.
4. Softener sheets can cause a waxy build-up on the lint screen. Wash the lint screen in warm soapy water and dry it completely before replacing it in the dryer.
5.Do not leave damp items in a warm or hot dryer --- start the drying cycle immediately and keep the exhaust opening clutter free.
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