Class D fire - These involve combustible chemicals and metals such as sodium, potassium, titanium,
magnesium, zirconium, and phosphorous.
PART C CHARACTERISTICS AND SOURCES OF FIRE AND SAFETY
HAZARDS
Vapor Characteristics.
In a fire, it is the vapor that actually burns. Characteristics of vapors
include:
Vapors are heavier than air and collect in low areas.
Vapors will hang low to the ground and spread over large areas.
On hot humid days vapors are produced in greater volume.
When vapors are allowed to collect, flashbacks can occur as the vapors come in contact with a heat
source and the heat travels back to the source of the vapors, causing a fire and possibly an explosion.
A 1- to 8-percent ratio by volume of vapors when mixed with air, will form an explosive range. An
explosive range is that point where the vapor and the air mixture will burn. A mixture above 8 percent is
too rich in vapors and will not ignite. A mixture below 1 percent is too lean in vapors (too rich in air) and
will not ignite.
Control of Vapors.
Empty containers (5 gallon, 55 gallon) that have previously contained petroleum product are more
dangerous than full ones. Fill such containers as soon as possible, or when they are stored empty,
ensure caps and bungs are on tight.
Store containers that have fuel in them or containers that previously contained product in a safe area.
Do not overfill or fill containers at too fast a rate as vapors will be displaced to the atmosphere and
become a hazard.
Repair leaking pipes and containers as soon as possible.
Clean up spills immediately (as long as the contamination is present, vapors are a hazard).
Sources of Ignition.
A source of ignition can be either a flame, spark, or other heat-generating
source. Some of the most common causes of heat are:
Smoking material (matches, lighters, and cigarettes).
Sparks (static electricity, moving fuel, moving equipment, welding and cutting).
Spontaneous combustion (oxidation and chemical reaction).
As a minimum, you should post "No smoking within 50 feet" signs in critical areas of the facility and enforce
the rule. Other precautions should also be observed/practiced, such as:
Designate all smoking areas at least 100 feet away from refueling operations.
In very hazardous areas, collect smoking materials at the entrance to the facility and keep them in
separate airtight containers at the entrance to the facility.
Welding and grinding should only be done under controlled conditions (that is, fire department notified,
vapor freeing completed, or when product in a pipeline is moving).
Electrical equipment must be maintained in safe working condition (approved electrical fixtures), and
grounding and bonding procedures must be utilized to minimize static electricity and arcing.
Ensure dispensing and receiving equipment is bonded and grounded.
Bottom load whenever possible, as top loading generates static electricity and splashing while filling.
Ensure that all personnel involved in gaging activities are trained to always bond themselves before
gaging storage tanks and tank vehicles.
Before gaging and sampling, allow a minimum of 30 minutes for the static charge to dissipate from fuel
receipts.
Always ensure that all fire extinguishers are in place and are operational.
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QM 5097
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