Fire hazards related to paint and varnish industries

Excerpt: PAINT is a common product we all have in our homes that can become a household hazardous waste when it is not properly stored or disposed. Paints are used extensively in many fields.

PAINT is a common product we all have in our homes that can become a household hazardous waste when it is not properly stored or disposed. Paints are used extensively in many fields. Today, paints are used for interior and exterior house painting, boats, automobiles, planes, appliances, furniture, and many other places where protection and appeal are desired.

The Indian Paint industry, estimated to be a Rs.21,000 Cr. industry, has been growing at a rate of above 15% for the past few years. The organized players of the industry cater to about 65% of the overall demand, whereas the unorganized players take care of the remaining 35%, in value terms. The unorganised players mainly dominate the distemper segment.

Hazards in paint industries

As per First schedule of Factories Act 1948, Section 2(cb) Paints and pigment industries are listed as hazardous process. There are specific responsibilities of the occupier in relation to hazardous process which are indicated in Maharashtra factories rules 73-V, 73-W, 73-X, 73Y, 73Z.

I) Fire hazard ;

If flammable solvents are used in your plant, it is a life-and- death matter to eliminate sources of ignition to prevent fires and explosions — both where the solvents are used and where they are stored. Your local's health and safety committee should conduct routine inspections of departments which use these solvents. There are four major types of fire hazards to look out for: to eliminate the fire hazards following precautions are recommended

  • Eliminate all open flames in the area. For example, look out for gas pilot lights in the area, welding operations (either routine or maintenance), lighted matches or cigarettes.
  • Avoid heat build-up. Make sure there are no ovens nearby, or heat lamps, or heating elements in electrical appliances. Any process which might result in hot cinders or glowing metals could ignite flammable solvent vapors. Even overheated bearings have been known in the past to ignite vapors.
  • Eliminate sources of sparks. Short circuits in electrical switches, electric motors and frayed electrical wires can cause fires — this requires regular site monitoring. Auto or diesel engines can emit sparks in their exhaust. Also sparks can be generated by static electricity — for example, from metal tools or when pouring flammable liquids from one metal container to another. To avoid sparks when pouring, it is important to ground each of the metal containers, or at least to bond them with an electrical wire and metal alligator clips before pouring.

Other controls

  • The key to reducing exposure to solvent vapors is having a good exhaust ventilating system, with the vent hood as close to the vapor source as possible. Other important measures include:
  • Store solvents in a proper, enclosed safety storage cabinet.
  • Transfer solvents in capped labelled containers. Don't let solvents sit out in uncovered containers.
  • Make sure solvent spills are wiped up promptly and store rags or absorbent materials in closed containers.
  • Make sure management provides you with proper safety clothing and chemical goggles.
  • Check whether other, safer solvents can't be substituted for those now in use.

National Fire Protection Association,( NFPA)

The most common causes of fire in spray painting operations are a result of improper separation of the paint booth from other areas using ignitable equipment--welders, grinders, cutters-- and electrical equipment. NFPA Standard 33 outlines the safety requirements for paint booths and is included in the Occupational Health and Safety Administration (OSHA) standards. These standards must be followed closely to avoid fire- and breathing- related injuries at work.

Location

According to the National Fire Protection Association and OSHA, paint booths must be completely separated from all other operations and located at least 20 feet from any combustible materials. Both also require paint booths to have a separate, approved sprinkler system, a fire rating of at least two hours and be built according to certain construction standards.

Construction

Paint booths must be made of concrete, masonry or supported and secured steel. Another noncombustible material, like aluminum, is acceptable for low-volume operations. All materials used in constructing paint booths must be noncombustible including those used in the connecting air supply. The booths must also be designed for safe, easy cleaning and so that fumes will sweep toward the exhaust. More specifics on paint booth construction are found in OSHA standards 1910.94(c) and 1910.107.

Electrical

All electrical and combustible materials inside the booth and within 20 feet of the booth are covered under OSHA standards. Only fixed lighting enclosed in protective panels and portable lamps approved for hazardous Class I locations may be used in spray booths. This includes all lighting outside of the booth within 20 feet. All open flames, heat and spark producing equipment must be kept 20 feet from the booth unless separated by a partition. Inside the booth, electrical wiring and equipment must also be approved for hazardous Class I, Division 1 locations. Wiring and electrical equipment outside the booth but within 20 feet must be approved for hazardous Class I, Division 2 locations. Finally, all metal parts of the spray booth must be properly grounded.

Ventilation

Paint booths must be equipped with a mechanized ventilation system to remove harmful fumes and airborne residues from the booth. Air exhaust may not be recirculated and must be directed away from the booth's air intakes. The exhaust discharge clearances set by OSHA must be followed carefully to prevent fire hazard and harmful fumes. All of the parts of the ventilation system-- the independent exhaust, fans, motors, belts and exhaust ducts--must be compliant with OSHA rule 1910.94(c)(5). Adequate ventilation must also be provided for painted items to dry to prevent the buildup of explosive fumes.

Velocity and Air Flow

OSHA standard 1910.94(c)(6) specifies the minimums for air velocities in spray booths according to the specific operation and size of the booth. Refer to OSHA's table G-10 on this standard, when designing the booth. In addition, harmful fumes must be diluted to 25 percent of their lower explosive limit as presented in the tables under OSHA standard 1910.94(c)(6)(ii) and table G-11. A compliant air-supplied respirator must be provided for workers downwind from the item being sprayed. Doors must be closed during spray painting.

Make-up Air

The paint booth must be supplied with new, clean air equal to the amount exhausted from the booth. Any doors that supply this air must be left open during spraying and the velocity may no be more than 200 feet per minute. The air may not be heated from within the booth. More specific regulations for each operation may be found in OSHA standard 1910.94(c)(7).

Baffles and Overspray Collectors

Overspray filters and distribution and baffle plates must be made of noncombustible material, properly installed and located for easy cleaning, inspection and replacement. All collecting tanks and systems must be constructed according to OSHA standard 1910.94©.

Fire Hazards of Spray Finishing with Flammable Liquids

The Hazard

Spraying with flammable liquids (paints) is a topic that needs to be revisited frequently. Although best practice standards- of which National Fire Protection Association (NFPA) 33 is considered the “bible”- have been around for decades now, still many people do not understand or implement proper controls.

The term “flammable liquid” is defined by NFPA as a liquid that emits vapours less than 100°F and that sustain combustion (the term that defines this process is “flash point”). Several factors make flammable vapours dangerous:

  • The low flash point means that unlike liquids with higher flashpoints, they do not need to be exposed to a heat source in order to be ignited.
  • Most common flammable liquids the vapours are heavier than air and therefore sink to floor level and tend to disperse less readily.
  • The vapours burn very quickly in what is called a “deflagration”- essentially an explosion. They also have a very high heat release.
  • Fires are difficult to extinguish. Water can be used to extinguish, but non water-miscible liquids will present more hazards (such as floating puddles of flammable liquids ready to spread the fire elsewhere).

Common flammable liquids include petroleum or alcohol-based paints and coatings, lacquers, mineral spirits, thinner, turpentine, kerosene, methyl ethyl ketone, and toluene.

Ignition Source Control

All electrical systems near the spray booth should be designed to prevent inadvertent ignition of flammable spray vapors. All electrical and lighting fixtures within a twenty feet horizontal or ten feet vertical distance from the booth need to be protected in accordance with NFPA 70 NFPA 70 'National Electric Code'. NFPA 70 'National Electric Code' specifies that Class I, Division 1 & 2 electrical should be installed.

Ventilation

The purpose of ventilation is to prevent accumulation of vapors. The best way to do this is with a spray booth. The booth should be mechanically exhausted to have a cross-sectional airflow of 100 feet per minute (CFM) in order to remove the flammable vapors. It is also imperative to maintain the concentration of vapour in the exhaust air stream below 25 percent of the lower flammable limit. This requires a sufficient flow of air moving through the booth at a sufficiently high velocity.

Note that the equipment (fans) that moves the vapors must not themselves be an ignition source, therefore, they should be constructed of non-ferrous metals or other non-spark generating materials.

Equipment (spray guns) should be interlocked with ventilation of the booth in order to assure that the ventilation is on (and take possible human error out of the process). This may go without saying, but the air must be exhausted safely outside the building (make sure all “clean-air” / EPA regulations are adhered to by filtering/scrubbing the air).

Fire Suppression

The area/booth should have fire suppression- either automatic sprinkler protection or automatic fire suppression (such as an FM-200 chemical extinguishing system). Despite good dilution, ignition source control, and human element factors, a fire can still develop. Make sure that nozzles are protected from overspray of paint (approved cloth bags can be used, however, make sure they are clean). It is also recommended that sprinkler heads or fire suppression nozzles be located within ductwork (e.g. leading outside).

Paint Storage

Make sure that all flammable liquids (paints) are stored in accordance with NFPA 30 Storage of Flammable Liquids. These can be in an approved storage room or in Underwriters Lab (UL) listed containers (there is a limit though). A small supply (generally less than 25g) can be in use outside the storage, but it should be placed in safety cans (UL/FM approved).

Human Element

Last but not least, the controls that rely on the operator are also very important. These include:

  • Equipment and storage containers should be bonded and grounded to prevent static electricity build-up (ignition source).
  • There should be a regular documented cleaning schedule to prevent excessive accumulations of overspray residue. Use of non-spark generating materials.
  • Filters should be changed regularly. There are various means of filtering the air, but the most common is non-woven cloth filters. Check airflow gauges to make sure the filters are not blocking airflow (usually due to clogged filters).
  • Previously used rags should be placed in self-closing cans during the day, and removed to a safe location outside the building at the end of the working shift.
  • Any portable fans or radios that are not in accordance with NFPA 70 (class I electrical) should not be used within the distances given above (this is a common violation).
  • Though this article concentrated on the fire/property hazards, the health hazards are also critical. Appropriate respirators and personal protective equipment (clothing, eyewear, etc.) should be used by employees. If lead or other metals are involved, there may need to be a further OSHA- required controls.

About Author

V.R. Bhide (Safety Professional)

Corresponding author:** Christiane Cova-Hög, Evonik Industries AG, T+49 201 1733050 christriane.cova-hog@evonik.com

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