Course 601 - Essentials of Occupational Safety and Health

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Flammable and Combustible Liquids

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Flammable and combustible liquids are, in short, liquids that can burn.

OSHA standard 29 CFR 1920.106 addresses the handling, storage, and use of flammable and combustible liquids. Flammable and combustible liquids are, in short, liquids that can burn. They are classified or grouped as either flammable or combustible by their flashpoints.

  • Flammable liquids will catch on fire and burn easily under normal working temperatures.
  • Combustible liquids have the ability to burn at temperatures that are usually above working temperatures.

Flash Point

The flash point of the liquid is the temperature at which it gives off vapor sufficient to form an ignitable mixture with the air near the surface of the liquid or within the vessel used as determined by appropriate test procedure and apparatus.

  • Flammable liquids have a flash point below 100 degrees Fahrenheit. Ethyl ether, acetone, benzene, and toluene all have flash points below 73 degrees F. Hydrazine and styrene have flashpoints between 73 and 100 degrees F.
  • Combustible liquids have a flashpoint at or above 100 degrees Fahrenheit. Acetic acid, Naptha, Cyclohexanol, formic acid, and nitrobenzene have flashpoints between 100 and 199 degrees F.

Flammable Range

Commitment is time and money.
Flammable range.

When vapors of a flammable liquid are mixed with air in the proper proportions in the presence of a source of ignition, rapid combustion or an explosion can occur. The flammable range includes all concentrations of flammable vapor or gas in air, in which a flash will occur or a flame will travel if the mixture is ignited.

There is a minimum concentration of vapor or gas in air below which propagation of flame does not occur on contact with a source of ignition. There is also a maximum proportion of vapor in air above which propagation of flame does not occur. These boundary-line mixtures of vapor with air are known as the lower and upper flammable limits (LFL or UFL), respectively, and they are usually expressed in terms of percentage by volume of vapor in the air.

1. What is the term used to describe the temperature at which a liquid gives off vapor into the air sufficient to form an ignitable mixture?

a. Flammable Range
b. Flash Point
c. Combustion Temperature
d. Vapor Pressure

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Two Primary Hazards

Image of Primary Hazards.
The primary hazards associated with flammable and combustible liquids is fire and explosion.

The primary hazards associated with flammable and combustible liquids are fire and explosion. Flammable and combustible liquids are present in almost every workplace. Fuels and many common products like solvents, thinners, cleaners, adhesives, paints, waxes, and polishes may be flammable or combustible liquids. Everyone who works with these liquids must be aware of their hazards and how to work safely with them.

  • Flammable liquids will catch on fire and burn easily under normal working temperatures. At normal room temperatures, flammable liquids can give off enough vapors to form burnable mixtures with the air. As a result, they can be a serious fire hazard. Flammable liquid fires burn very fast. They also give off a lot of heat and often clouds of thick, black, toxic smoke.
  • Combustible liquids have the ability to burn at temperatures that are usually above working temperatures. Combustible liquids at temperatures above their flashpoint also release enough vapor to form burnable mixtures with the air. Hot combustible liquids can be as serious a fire hazard as flammable liquids.

Spray mists of flammable and combustible liquids in the air may burn at any temperature if an ignition source is present. The vapors of flammable and combustible liquids are usually invisible. They can also be hard to detect unless special instruments are used.

Most flammable and combustible liquids flow easily. A small spill can cover a large area of workbench or floor. Burning liquids can flow under doors, down stairs, and even into nearby buildings. Materials like wood, cardboard, and cloth can easily absorb flammable and combustible liquids. Even after a spill has been cleaned up, a dangerous amount of liquid could still remain in surrounding materials or clothing, giving off hazardous vapors.

2. Which of the following have the ability to burn at temperatures that are usually above working temperatures?

a. Flammable liquids
b. Explosive solids
c. Combustible liquids
d. Flammable solids

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Safe Use of Flammable and Combustible Liquids

Image of Primary Hazards.
There are many sources of ignition.

A good plan for the safe use of flammable and combustible liquids contains these components:

  • Control of the ignition sources.
  • Proper storage
  • Fire control methods
  • Safe handling

Possible Ignition Sources

Be sure to take adequate precautions when handling flammable and combustible liquids to prevent the ignition of flammable vapors. Some sources of ignition include:

  • Sparks from electrical tools and equipment.
  • Sparks, arcs and hot metal surfaces from welding and cutting.
  • Tobacco smoking.
  • Open flames from portable torches and heating units, boilers, pilot lights, ovens, and driers.
  • Hot surfaces such as boilers, furnaces, steam pipes, electric lamps, hot plates, irons, hot ducts and flues, electric coils and hot bearings.
  • Embers and sparks from incinerators, foundry cupolas, fireboxes and furnaces.
  • Sparks from grinding and crushing operations.

3. Sparks from grinding and crushing operations may be considered a possible _____ for flammable and combustible liquids.

a. exposure control
b. ignition source
c. storage issue
d. control measure

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Storage and Handling

Image of Primary Hazards.
Proper storage of flammable and combustible liquids will help prevent fires from occurring.

Containers

Proper storage and handling of flammable and combustible liquids will help prevent fires from occurring; only approved, closed containers for storage of flammable or combustible liquids may be used under OSHA rules. Such containers include safety cans or containers approved by the U.S. Department of Transportation.

A safety can is a container that has a self-closing lid, internal-pressure relief, and flame arrestor with a capacity of not more than 5 gallons. Inexpensive, plastic cans are not approved for use in roofing operations. However, manufacturers do sell plastic containers that meet the OSHA requirements for safety cans.

Flammable liquids that are extremely viscous, or difficult to pour, like single-ply adhesive, can be left in their original shipping containers. Similarly, OSHA allows the use of original containers of flammable liquids that are in quantities of one gallon or less.

Cabinets

Safety cabinets allow for greater quantities of flammable and combustible liquids to be stored safely inside buildings. Up to 60 gallons of a flammable liquid or as much as 120 gallons of a combustible liquid may be stored indoors in a safety cabinet. Each cabinet must be labeled "Flammable-Keep Fire Away." Up to three cabinets may be stored in one room. Without a safety cabinet, only 25 gallons of either flammable or combustible liquids are allowed to be stored inside a building.

Static Electricity

Static electricity may be generated when transferring liquids, gases, or solids through pipes or hoses. It is important to dissipate this electric charge when handling flammable and combustible materials. When transferring flammable or combustible liquids from one container to another, the two containers must be "bonded" together. The bonding process involves attaching a wire with alligator clips on each end to both containers. The clips must penetrate the container coating and touch metal. You may need to score the paint with the alligator clips.

To dissipate static electricity, the container receiving the liquid must be in contact with the ground and not insulated from contact with the ground. For example, plastic or composite pickup truck bed liners prevent the flow of static electricity to ground because the liner does not conduct electricity. The receptacle container must have a clear path to ground, by direct contact or use of a grounding strap or wire, to effectively eliminate static.

4. What is the term defined as a container that has a self-closing lid, internal-pressure relief, and flame arrestor with a capacity of not more than 5 gallons?

a. Approved container
b. GHS vessel
c. OSHA container
d. Safety can

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Ventilation

Safety glasses with side shields
Well-designed and maintained ventilation systems reduce risk.

Well-designed and maintained ventilation systems remove flammable vapors from the workplace and reduce the risk of fire and health problems. The amount and type of ventilation needed to minimize the hazards of flammable and combustible liquid vapors depend on such things as the kind of job, the kind and amount of materials used, and the size and layout of the work area.

An assessment of the specific ways flammable and combustible liquids are stored, handled, used, and disposed of is the best way to find out if existing ventilation controls (and other hazard control methods) are adequate.

  • Some workplaces may need a complete system of hoods and ducts to provide acceptable ventilation. If flammable vapors are likely to condense, the ducts should have welded joints. Other workplaces may only require a single, well-placed exhaust fan.
  • Use non-ferrous fan blades and shrouds, and explosion-proof electrical equipment in exhaust fan ventilation systems for these liquids.
  • Regular cleaning of the ventilation system will decrease the severity of any fires and will reduce the likelihood of spontaneous combustion if some self-heating material is present.
  • Ventilation equipment used to handle solvent vapors should meet the relevant fire code requirements.

5. Ventilation systems for flammable or combustible liquids should use exhaust fans with _____.

a. painted metal covers and blades
b. non-ferrous fan blades and shrouds
c. grounded fan blades and covers
d. fire-proof equipment

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Personal Protective Equipment (PPE)

Safety glasses with side shields
Safety glasses with side shields need to be worn when handling flammable or combustible materials.

Skin and eye contact should be avoided when working near flammable or combustible liquids. To make sure injury to eyes and skin does not occur, wear safety glasses with side shields, laboratory coats (coveralls are acceptable in shop settings), and closed-toe shoes. This is only minimum protection and must be upgraded if necessary.

Additional Personal Protective Equipment (PPE) such as chemical goggles, face shields, chemical aprons, and chemical resistant gloves and respiratory protection must be worn if there is a chance of exposure to flammable or combustible liquids above OSHA's Permissible Exposure Limit (PEL). The PEL is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise.

An emergency eyewash and safety shower should be located in all areas where flammable or combustible liquids are used. If there is skin or eye contact, then flush the affected area for at least 15 minutes and report to your employer for evaluation and treatment.

6. Which of the following additional PPE may be required when employee exposure to flammable or combustible liquids is above OSHA's PEL?

a. Open-toe shoes
b. Nose plugs
c. Dust masks
d. Respiratory protection

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Fire exit sign
In emergencies like chemical fires and spills, act fast. Leave the area at once if you are not trained to handle the problem.

What about emergencies?

Even if employees take all the necessary precautions to protect themselves from hazardous material spills, they still need to be ready to handle emergencies safely. In emergencies like chemical fires and spills, act fast.

  • Leave the area at once if you are not trained to handle the problem or if it is clearly beyond your control.
  • Alert other people in the area about the emergency.
  • Call the fire department immediately.
  • Report the problem to the people responsible for handling emergencies where you work.
  • Obtain first aid if you have been exposed to harmful chemicals and remove all contaminated clothes.
  • Emergency eyewash stations and safety showers should be present wherever accidental exposure to materials that can damage skin or eyes might occur.
  • Only specially trained people, equipped with the proper tools and protective equipment, should handle the emergency. Nobody else should go near the area until it is declared safe.

7. What should the employer have available wherever accidental exposure to materials that can damage skin or eyes might occur?

a. First-aid creams and bandages
b. Emergency eyewash stations and safety showers
c. Water hose-down facilities
d. Emergency phones and oxygen masks

Check your Work

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Napo in... Danger: chemicals! - episode 004 - Flammable. Know more about Napo.

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