Written by: Dr. Adam Marty

This consultant’s corner pertains to industry operations that apply “flammable and combustible finishing materials when applied as a spray by compressed air, “airless” or “hydraulic atomization,” steam, electrostatic methods, or by any other means in continuous or intermittent processes.” This article also pertains to operations that apply “combustible powders by powder spray guns, electrostatic powder spray guns, fluidized beds, or electrostatic fluidized beds.”  This language comes from the scope of the OSHA spray finishing standard, CFR 1910.107.  In summary, this language addresses operations of a company that sprays or applies an aerosol that will ignite, either as it is applied or after it has dried. However, the standard “does not apply to outdoor spray application of buildings, tanks, or other similar structures, nor to small portable spraying devices not used repeatedly in the same location.”

Spraying with flammable and combustible liquids and powder coating operations present unique hazards.  Fires, explosions, deflagrations, and hazardous and toxic atmospheres are a concern.  The OSHA spray finishing standard has requirements for spraying operations, however, the standard does not provide the most current requirements for these operations.  The National Fire Protection Association (NFPA) 33: “Standard for Spray Application Using Flammable or Combustible Materials” provides arguably the most authoritative guidance on these types of operations, and especially, powder coating operations.

Many employers who spray paints containing flammable solvents, such as toluene, are aware of the fire hazards associated with this operation and have implemented appropriate controls, such as conducting spraying within a booth.  However, some confusion exists where latex or water-based paints are sprayed.  Although, the liquid spray may not ignite, the dried spray or residue may be capable of being ignited.  If the dried residue can be ignited, the OSHA standard applies to the spraying of latex or water-based paints.

Even more confusion exists with powder coating operations.  An example is the need to protect the spray area within a spray booth with an automatic fire suppression system.  This confusion may exist because the OSHA spray finishing standard lacks specific detail regarding this type of operation.  Many manufacturers of powder coating booths do not normally equip booths with an automatic fire suppression system.  It is important to keep in mind that the OSHA spray finishing standard is based on an old NFPA standard (NFPA 33 Spray Finishing, 1969).  Most powder paints are combustible (i.e. ignitable) and they are usually sprayed.  Therefore, most powder painting will fall within the scope of the OSHA standard.  Current NFPA 33 clearly states in its scope that the standard applies to processes in which combustible dry powders are applied.  The scope of current NFPA also includes the “spray application of water-borne, water-based, and water-reducible materials that contain flammable or combustible liquids or that produce combustible deposits or residues.”  In all cases, the employer should examine their safety data sheets to determine if the material being sprayed or applied is flammable or combustible, or if it contains flammable or combustible ingredients.  If in doubt, the manufacturer of the material should be consulted and provide responses in writing.  OSHA can always issue a general duty clause citation and reference a consensus standard, such as the NFPA.  For a general duty violation, four criteria need to be met.  The first criteria includes that the employer failed to keep the workplace free of a hazard (e.g. using a flammable or combustible material in an unsafe manner) to which employees were exposed.  The second criteria is that the hazard was recognized (e.g. knowledge from reading this article or other related literature).  The third is that the hazard was causing or was likely to cause death or serious physical harm (e.g. fire resulting from negligent use of such materials).  The fourth criteria is that there was a feasible and useful method to correct the hazard (e.g. installation of a fire suppression system).  The OSHA and the NFPA regulations are intended to protect lives.

OSHA has some specific requirements for spray finishing operations using flammable and combustible materials.  Generally the requirements include booth design and construction and electrical equipment approved for a hazardous location.  Further requirements include other sources of ignition, ventilation, flammable and combustible liquid handling and use.  Also covered include fire protection, requirements related to operations and maintenance, powder coating operations, and electrostatic processes to name a few.

Having evaluated several spray finishing operations by this consultant, the following were some of the more common hazards observed:

• Failing to maintain a device that indicates the ventilation system is functioning properly. OSHA requires a device, such as a gauge, be installed to indicate or insure that the required air velocity is maintained.
• Lack of an adequate automatic fire suppression system where dry-type filters are used, such as with an automotive spray booth or powder coating booth. OSHA requires an approved automatic sprinkler system in the space within the spray booth on the upstream and downstream sides of filters.
• Existence of electrical equipment installed within the spray area (i.e. spray booth, spray room, or spray area) that is not approved for a hazardous location. A Division 1 area generally exists where a flammable or combustible atmosphere is likely to exist under normal operating conditions.  A Division 2 area extends beyond the Division 1 area, its limits depending on several variables.  The Division 2 area exists where a flammable or combustible atmosphere could exist under abnormal operating conditions.  In both cases, electrical equipment within these areas must be approved for the location.
• Failing to effectively ground all metal parts within the booth. OSHA requires all metal parts of spray booths, exhaust ducts, and piping systems conveying flammable or combustible materials be properly grounded in an effective and permanent manner.  NFPA also requires electrical grounding within spray rooms and spray areas, as well as grounding of personnel. A static discharge could ignite a flammable or combustible atmosphere.
• Transferring flammable or combustible liquids from one container to another without first bonding and grounding the containers. OSHA requires that both containers be effectively bonded and grounded to prevent discharge sparks of static electricity.
• Excessive residues present within the spray booth, room, or area. OSHA requires that these areas be kept as free as practical from the accumulation of deposits of combustible materials.  The tools used for cleaning these deposits must also be of non-sparking material.  The spray area can be demarcated where the combustible residues occur, which affects electrical classification.  If the residue can be easily collected, it is probably excessive.  The residue could also be sent to a laboratory for a combustibility analysis.
• Failing to maintain an approved metal waste can for disposing of rags or waste impregnated with finishing material. Rags or waste impregnated with finishing material can spontaneously combust.  Making an approved metal waste can available is an OSHA requirement and it should be readily available to employees.
• Failing to post “No Smoking” signs in the spray areas and paint storage rooms. The letters should be in large letters on contrasting color background and conspicuously posted.
• Failing to keep the powder coating area free of the accumulation of powder coating dusts and particularly on horizontal surfaces. Like combustible paint residues, this too can be used to demarcate your spray area
• Performing housekeeping activities in such a manner that disperse or re-aerosolize the powder paint. The use of an ordinary shop-vac would be an example of an ineffective housekeeping technique.  The filters of an ordinary shop-vac do not provide enough filtration efficiency to remove all dust.  This type of vacuum is also not approved for a hazardous location.  There could be a combustible concentration of dusts within the vacuum system.

If you know the OSHA spray finishing standard applies to your operation, it is recommended that you read and become familiar with the applicable requirements of both CFR 1910.107 and NFPA 33.  This brief overview only addresses some of the major requirements of this OSHA standard.  More detail is provided by reviewing each of these standards.  NFPA is available to read online for free.  There is also a decent checklist for operations involving flammable and combustible liquids available at https://www.cdc.gov/niosh/docs/2004-101/chklists/n40spr%7E1.htm.  If operations include the types of hazards described above in ones workplace, the USF SafetyFlorida Consultation program can be consulted for a more comprehensive evaluation for worker safety and health.