Greetings to Members of Western States Roofing Contractors Association:
WSRCA’s Industry Issues Committee is responding to reports from Member Contractors in the Western U.S. by preparing the following Information Bulletin regarding on-roof fires that have been caused by static electrical sparks during the application of single-ply membrane roofing using solvent-based adhesive.
Solvent-based adhesives may release fumes when their pails/containers are open and during application that can be a potential fire hazard during specific conditions and/or situations. A spark is all that is required, under certain conditions, to ignite such fumes. During dry outdoor ambient conditions, sparks can be caused by static electrical discharge. These three conditions can come together during a single-ply roofing installation and unexpectedly start a fire. Reports from the field indicate that this has been the case for more than one contractor recently, especially when weather conditions have been conducive to static electricity.
Reports from the field indicate that when relative humidity is very low, whether it be during cold, dry weather, or hot and dry weather, static electrical charges can build up during insulation roofing application. Most reports have involved steel roof decks and faced polyisocyanurate roof insulation and single-ply roofs. Static charges can be created when weather conditions are right and rigid foam insulation boards are slid or dragged across each other, when membrane sheets are moved over the installed insulation or over other thermoplastic roof membrane sheets, and just from walking on the insulation or insulated roof. If static charges have accumulated, spark(s) may occur when the metal bar of the adhesive roller or applicator handle touches the metal adhesive pail or container, or even when a worker’s skin or hand touches metal. Sometimes these sparks result in ignition of adhesive fumes and/or the adhesive itself during application. There are measures to be taken to help prevent the build-up of static charges, such as: by confirming that the existing building or building-under-construction is grounded, by taking care regarding how materials are moved and placed on the roof, wearing all cotton rather than synthetic clothing, walking carefully without shuffling, grounding equipment being used on the roof, just to name a few.
However, reports from the field where fires have occurred indicate that it is very important that the crew understand how to respond to and extinguish on-roof fires as soon as possible when they occur. It is also important for the contractor to be aware of the weather conditions that may ead to static build-up. Cold and dry winter weather is commonly associated with static build up, but if relative humidity is very low build up can also occur during hot, dry weather.
We note that this issue is not being discussed much in the roofing and waterproofing industry. However, please be aware that the issue of static-electric spark problems is mentioned by the manufacturers of adhesive application equipment, it is also referred to in OSHA bulletins, and has been mentioned in articles published in NRCA’s Professional Roofing magazine. Thorough descriptions of the problem as it relates to single-ply roofing, however, are lacking, and detailed solutions have not yet been presented.
This issue has come to our attention solely through reports from the field. To date, the information we have is mainly from three (3) different WSRCA Member Contractors working in the Western U.S. However, the popularity of insulated single-ply roof systems in the Western U.S. creates a growing potential for this problem to occur, and WSRCA wants to be sure it’s members are aware of the potential hazard and can then be better prepared to prevent the potential for fires on their projects, as well as be prepared to minimize the potential damage to persons, property and potential lack of calm-handling of the situation and/or potential injury to unaware roofing technicians.
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