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  • U.S. Department of Labor
  • Occupational Safety and Health Administration
  • Directorate of Technical Support and Emergency Management
  • (formerly Directorate of Science, Technology and Medicine)
  • Office of Science and Technology Assessment

Hazards of Using Flammable Liquids in Cutting Laminated Glass


Safety and Health Information Bulletin

SHIB 10-06-2008

This Safety and Health Information Bulletin is not a standard or regulation, and it creates no new legal obligations. The Bulletin is advisory in nature, informational in content, and is intended to assist employers in providing a safe and healthful workplace. Pursuant to the Occupational Safety and Health Act, employers must comply with hazard-specific safety and health standards and regulations promulgated by OSHA or by a state with an OSHA-approved state plan. In addition, pursuant to Section 5(a)(1), the General Duty Clause of the Act, employers must provide their employees with a workplace free from recognized hazards likely to cause death or serious physical harm.

Purpose

The purpose of this Safety and Health Information Bulletin (SHIB) is to inform employers and their employees of the associated hazards involved in cutting laminated glass using flammable liquids and of ways to eliminate or reduce the risk of injury such as:

  1. Use methods that do not involve flammable liquids when cutting laminated glass.
  2. Provide appropriate personal protective equipment (PPE) and instructions regarding its use.
  3. Ensure that flammable liquids are stored in and dispensed from approved containers and are safely handled to the point of final use.
  4. Provide information, instruction, training, and supervision to employees regarding safe work practices to be used in cutting laminated glass.

Background

Laminated glass, also known as safety glass, consists of two or more layers of ordinary annealed glass bonded together with a plastic interlayer, usually Polyvinyl Butyl. This interlayer keeps the outside layers of glass bonded even when they are broken, preventing the glass from breaking into large, sharp pieces, and providing some degree of sound insulation. Safety glass is often used for shop fronts and windshields. The thickness of safety glass can vary from approximately 6 mm to as thick as 50 mm for bullet resistant glass.

The practice of cutting laminated glass involves first scribing both sides of the glass with a glass cutter. Denatured alcohol or another flammable is then dripped into the scribed crack and ignited with a lighter or match causing the butyl substrate or interlayer to melt. The employee then uses a rocking motion to further separate the glass and completes the cut using a utility knife.

On September 17, 2004, the OSHA Allentown, Pennsylvania Area Office investigated an accident which involved cutting laminated safety glass using a flammable liquid. The accident resulted in second- and third-degree burn injuries to an apprentice employed at a glass installer. He was pouring alcohol from a partially full gallon container when the alcohol ignited and exploded. Apparently, a vapor trail of the alcohol ignited and then flashed back to the container.

The explosion knocked out a ceiling light and covered the employee with the remaining alcohol. The investigation revealed that the container had been compromised by a hole in the metal screw cap. The hole appeared to have been made with a nail (See Photos #1 and #2).

Photo #1: Hole punched into the cap of the can to pour flammable liquid.

Photo #1: Hole punched into the cap of the can to pour flammable liquid.

Photo #2: Gallon can of alcohol showing damage from the explosion.

Photo #2: Gallon can of alcohol showing damage from the explosion.

The factors that contributed to this accident included the use and alteration of a container which was not designed to safely dispense the flammable liquid, the lack of flame-resistant personal protective equipment, the lack of adequate ventilation, and the lack of proper instruction and supervision of the employee. In addition to this case, OSHA’s IMIS database identified eight other accidents where employees received second-and third-degree burns while cutting laminated glass. In two of these cases, the employee died as a result of his burns. During such operations, OSHA requires that containers be approved (29 CFR 1910.106(d)(2)(i)). When not in use, flammable liquids must be kept in approved covered containers (29 CFR 1910.106(e)(2)(iv)(a)).

During use there must be no open flames or other sources of ignition within the possible path of the vapor travel (29 CFR 1910.106(e)(2)(iv)(c)). OSHA also requires that employees wear adequate protective clothing appropriate to the risk and that they are adequately trained to safely perform the work (29 CFR 1910.132(a) and 29 CFR 1910.132(f); and 29 CFR 1910.1200(h)).

OSHA is concerned about the continued occurrence of these significant injuries in what appears to be a common work procedure. Due to the potential for employees to sustain serious if not fatal injuries, the use of flammable liquids to heat and cut laminated glass is discouraged and should be avoided. An emphasis should be placed on using alternate methods of cutting and ensuring that the following OSHA requirements and recommendations for hazard control are adhered to.

OSHA Recommended Work Practices and Requirements

  1. When cutting laminated glass, use methods that do not involve flammable liquids. For example, use special purpose laminated glass cutting tools and tables, standard carbide cutting wheel techniques, vertically-inclined saw frames, abrasive high pressure waterjets or hot air blowers for heating the plastic interlayer of the safety glass.
  2. Provide adequate information, instruction, training and supervision to all employees to ensure that safe work practices are in place and followed.
  3. Conduct a hazard assessment of the workplace (29 CFR 1910.132(d)).
  4. Containers holding any hazardous substances must be labeled with the identity of and appropriate hazard warnings for the chemical (29 CFR 1910.1200(f)).
The use of flammable liquids to cut laminated safety glass is strongly discouraged and should be avoided. Adherence to applicable OSHA regulations and following the safe work practices for handling flammable liquids described in this SHIB will help employers minimize the potential for serious or fatal injuries to their employees.

Safety Precautions When Handling Flammable Liquids

  1. Engineering controls such as ventilation must be used when necessary to maintain airborne levels of contaminants below the Permissible Exposure Limits (PELs) and to otherwise prevent accumulation of hazardous vapors, including flammable vapors (29 CFR 1910.1000(e)).
  2. Employees must wear personal protective equipment designed and constructed for the work to be performed (29 CFR 1910.132 and 29 CFR 1910.133). For additional information see NFPA 2113 - Standard on Selection, Care, Use, and Maintenance of Flame-Resistant Garments for Protection of Industrial Personnel Against Flash Fire, or an equivalent standard.
  3. When dispensing denatured alcohol or any flammable liquid, ensure that employees use an "approved" container, such as a safety can, which will prevent the ignition of the flammable liquid contained within it (29 CFR 1910.106(e)(2)(iv)(d)). Additionally, the device and procedure should limit the amount of flammable liquid used to only that required to safely perform each cut.
  4. Ensure that employees are aware that alcohol burns with a flame that appears clear in bright light, making it difficult to see the flame and its path of travel. Consequently, an employee may not see the flame and pour additional flammable liquid onto it.
  5. A safety can is a container "approved" or listed by a nationally recognized testing laboratory (29 CFR 1910.106(a)(35) and 29 CFR 1910.7). It is of not more than 5 gallons capacity and so designed that it will safely relieve internal pressure when subjected to fire exposure. Safety cans normally have several basic design qualities including:
    1. a spring-loaded cap that closes the spout automatically when released. The spring tension in the cap must be designed to lift the cap in the event of excessive internal vapor pressure and to prevent the container from rupturing or exploding;
    2. a spout that is equipped with a flame arrester screen designed to prevent outside fire from reaching the flammable liquid inside the container. (With the screen in place, the vapors will burn around the spout, but will not permit an internal fire or explosion. This screen must not be removed or damaged.) See Factory Mutual Engineering Corp. Approval Standard for Safety Containers and Filling, Supply and Disposal Containers (Class 6051/6052 - May 1976).
  6. Ensure that flammable liquids are used only where there are no open flames or other sources of ignition, other than the process igniter, within the possible path of vapor travel (29 CFR 1910.106(e)(2)(iv)(c)). Wherever possible, a piezoelectric or equivalent controlled igniter should be used.
  7. The flammable liquids container should be removed from the area near or around the cutting prior to igniting the liquid. Similarly, other flammables or combustibles should also be removed.

Conclusions

Minimizing the potential for serious or fatal injuries to employees is the primary concern of this SHIB. Using safer alternate methods, adherence to applicable OSHA regulations and following the safe work practices described in this SHIB will help accomplish this goal.

  • Edwin G. Foulke, Jr.
  • Assistant Secretary
  • Occupational Safety and Health Administration
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