Use and dispensing of flammable and combustible liquids presents fire and explosion hazards to facilities and occupants. When these liquids are transferred (i.e., poured, pumped, or agitated) from one metal container or a special conductive plastic container to another, the movement of the liquid may generate static electricity. An accumulation of static electricity can discharge with enough energy to lead to a “spark” which can ignite the flammable vapors likely to be present during dispensing operations.
Proper grounding and bonding limits the potential of static electrical spark during dispensing procedures. For prevention of sparks, all dispensing components (containers, piping, funnels, pumps) must be electrically connected to a static grounding system using bond wires, conductive materials and ground cables and attachments. Grounding and bonding measures must be applied to any shop, research and/or lab location where open use and dispensing of flammable liquids from large containers may occur. For the purposes of this policy, large containers are defined as greater than 4L
Please note:
• Bonding and grounding are required for the containers that conduct electricity, such as those made from metal or conductive plastics. If a container is made from a material that does not conduct electricity, such as polyethylene plastic or glass, then it cannot be grounded and bonded unless using a grounded metal fill tube/funnel or grounding rod. Nonconductive containers shall not be used for transfers greater than 4L. Please reference the attached decision tree.
• If dispensing a flammable/combustible chemical from a ≤ 4L container, then grounding and bonding is not required. Dispensing of flammable liquids of this volume will ideally be performed in a certified chemical fume hood.
Reach out to UK Occupational Health and Safety at (859)257-2924 for an assessment prior to completing any grounding or bonding.
Flammable liquid: According to the Globally Harmonized System (GHS), this class of chemicals has a flash point at or below 199.4oF (93oC), allowing it to easily ignite at ambient temperatures. This policy applies to chemicals designated as GHS Flammable Categories 1, 2, or 3. In other words, this policy applies to flammable chemicals with flashpoints below ≤ 100⁰F. This information is located in either Section 2 (Hazard Information) or Section 9 (Flashpoint information) of the chemical manufacturer’s Safety Data Sheet.
Bonding refers to ensuring all components (containers, piping, pumps, funnels) in the dispensing process carry the same electrical potential. In other words, this means ensuring all conducive components in the dispensing process are connected by a conductor.
Grounding is the process of carrying the electric charge to “earth” or “ground” to negate any electrical potential. Indoor dispensing locations can connect to the grounded building systems, such as the electrical distribution system, to carry the charge to ground.
Grounding is accomplished by attaching a ground cable to a ground rod or grounding system designed to provide a continuous ground path to less than 10 ohms (NFPA 77). The ground attachment must be metal-to-metal and must not be painted, and kept clean, free of debris or dirt to ensure a good connection.
Use appropriate bonding and grounding cables such as plastic coated 10’ coiled grounding cable with clamps on both ends, or braided 3’ bonding cable with alligator clips on both ends. Only metal containers should be used for flammable liquids in quantities > 4 L. Exception: plastic containers > 4L may be used for gasoline because the vapors are generally above the upper flammable limit making ignition less likely. Grounding floor mats should also be considered in areas with nonconductive flooring.
Plastic and glass containers larger than 4 L should not be used for flammable liquid dispensing operations as these materials are non-conductive. Where there is a chemical compatibility issue and metal containers cannot be used, a metal funnel and fill pipe that extends to the bottom of the container or a metal rod inserted into the container can be used for bonding and grounding the operation. Safety cans have a self-closing airtight lid, flexible metal dispensing nozzle and a flame arrestor that protects the contents from an external ignition source, making them safer for storage and dispensing of flammable liquids. However, bonding and grounding is still required when transferring flammable liquids because static electricity generation and accumulation is possible during the transfer. Polyethylene safety cans are equipped with a grounding lug designed to attach to ground wires.
Carefully assess and identify a safe location for flammable liquids transfer. Dispense flammable liquids (≤ 4 liters) inside a chemical fume hood or in a well-ventilated location. Flammable liquids in quantities >4L liters must be dispensed inside a room/area specifically designed for dispensing flammable liquids with explosion-proof electrical wiring and equipment, and special ventilation systems. Contact the UK Fire Marshal (859-257-6326) if you have questions. Ensure exit doors and egress pathways are not obstructed in the dispensing location. Ensure all ignitions sources (e.g., flames, electrical outlets, etc.) are located at least 3 feet away from dispensing operations.
Synthetic clothing, plastic aprons and rubber shoes are all insulating and can build up charge (10-30 mJ). Wear cotton clothing and close-toed, static dissipating shoes or perform work on an anti-static mat while dispensing. A flame-resistant lab coat, goggles, and protective gloves compatible with the chemical must also be worn. Removal of garments such as coats and sweaters should always be taken care of away from flammable areas.
National Fire Protection Association. Flammable and Combustible Liquids Code, NFPA 30.(n.d.) https://www.nfpa.org/education-and-research/research/fire-protection-researchfoundation/projects-and-reports/the-fire-risk-of-intermediate-bulk-containers/about-nfpa-30
Recommended Practice on Static Electricity. NFPA 77 (2024). (n.d.) https://www.nfpa.org/product/nfpa-77-recommended-practice/p0077code
Oregon Occupational Safety and Health. Flammable and combustible liquids . State of Oregon. (n.d.-b). https://osha.oregon.gov/pages/topics/flammable-and-combustible-liquids.aspx
Occupational Safety and Health Administration. 1910 Subpart H Hazardous Materials. 29 CFR 1910.106 https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.106
Stanford University. Bonding and Grounding Best Practices. Environmental Health and Safety (n.d.) https://ehs.stanford.edu/wp-content/uploads/24-119_Grounding_Bonding.pdf
University of Berkeley. Flammable liquid transfer guidelines. Office of Environment, Health & Safety. (n.d.). https://ehs.berkeley.edu/safety-subject/fire-safety/flammable-liquid-transfer-guidelines
University of California San Diego. Flammable and combustible liquids storage requirements. Environmental Health and Safety (n.d.). https://blink.ucsd.edu/safety/researchlab/chemical/liquids/storage/index.html#Bonding-andgrounding
University of Chicago. Grounding and Bonding. Environmental Health and Safety. (n.d.) https://safety.uchicago.edu/fire-life-safety/fire-safety/bonding-and-grounding/
University of Minnesota. Health, Safety, and Risk Management. (n.d.) https://hsrm.umn.edu/grounding-bonding-flammables
University of Washington. Grounding and bonding focus sheet. EHS. (n.d.). https://www.ehs.washington.edu/resource/grounding-and-bonding-focus-sheet-1173
Wayne State University. Safe transfer of flammable liquids: Grounding and bonding. Office of Environmental Health and Safety (n.d.). https://research.wayne.edu/oehs/lab-safety/grounding-bonding