Before work on the jobsite begins, a fire protection program should be in place.

Fire Extinguisher
A fire extinguisher is one of your first lines of defense in a small fire. If working on a multi-level structure, make sure there is access to an extinguisher on each floor. Extinguishers should be clearly-visible and easily-accessible. According to OSHA 1926.150(c)(1)(i), an extinguisher shall be provided for every 3,000 square feet of the protected building. In case of a fire emergency, any worker should be able to have access to an extinguisher within 100 feet. The extinguishers cannot be rated less than 2A. If this is not feasible, one 55-gallon open drum of water with two fire pails may be used as a substitute. In the winter, protect drums from freezing.

It is important to understand what hazards are dealt with on each site. Be sure to have correct extinguishers for the hazards that are present on site. Different trades bring different materials that may require specifically-rated fire extinguishers. 

Class A - Ordinary combustibles
Class B - Flammable liquids
Class C - Electrical appliances
Class D - Combustible metals
Class E - Flammable gases

If an incident occurs and an extinguisher is used, it must be serviced and refilled, regardless the amount used. Regular inspections of fire extinguishers are recommended to ensure they are fully charged and have not been damaged.

Proper Use of an Extinguisher
When using an extinguisher for a small fire there are four simple steps to follow. Remember to PASS:

Pull the pin at the top of the extinguisher. The pin releases a locking mechanism and will allow you to discharge the extinguisher. 
Aim at the base of the fire, not the flames. This is important! In order to put out the fire, you must extinguish the fuel.
Squeeze the lever slowly. This will release the extinguishing agent in the extinguisher. If the handle is released, the discharge will stop.
Sweep from side to side. Using a sweeping motion, move the fire extinguisher back and forth until the fire is completely out. Operate the extinguisher from a safe distance, several feet away, and then move towards the fire once it starts to diminish. Be sure to read the instructions on your fire extinguisher - different fire extinguishers recommend operation from varying distances. Remember: aim at the base of the fire, not the flames!

If the fire is not able to be put out with the extinguisher, sound the fire alarm, call the fire department, and evacuate the jobsite. Personnel safety is more important than product damage.

Housekeeping
Prevention is the key to success in avoiding and protecting against fire. Maintain a clean workstation. Store all indoor materials as to minimize the spread of fire and to allow easy access for firefighting. When stacking combustible material, do not exceed a height of 20 feet. Be sure that any materials on the jobsite do not impede exits in case of a fire. When storing outdoor materials, keep them away from the building at a distance of 10 feet or more. Keep proper clearance from any lights or heating units. Never have an open flame on site. When using temporary heaters in winter months, be sure to store them away from combustible materials. Inspect the surrounding area and clear out all brush, weeds, etc. that may pose a fire hazard. 

Hot Work/Welding
When performing hot work, remove all fire hazards. Before beginning work, be aware of all flammable vapors and combustible materials and remove hazards. Have appropriate firefighting equipment nearby. As a precaution, assign a fire watch to guard against fire while welding. The fire watch should be trained in fire extinguisher use and should have an extinguisher in their possession while hot work is being performed. They must also know where and how to sound the fire alarm. The fire watch will also be on guard 30 minutes after the hot work is completed to detect and extinguish any fire that may be smoldering.     

Sources
Fire Protection and Prevention for Construction

Additional Resources
WCF Insurance Safety Department
(385) 351-8103

Ask a Safety Consultant

osha.gov
cdc.gov/niosh

NOTICE: This guide may make reference to the Occupational Safety and Health Administration (OSHA) regulations; however the guide is not legal advice as to compliance with OSHA or other safety laws, codes, or regulations. Compliance with OSHA and other safety laws codes or regulations, and maintaining a safe work environment for your employees remains your responsibility. WCF Insurance does not undertake to perform the duty of any person to provide for the health or safety of your employees. WCF Insurance does not warrant that your workplace is safe or healthful, or that it complies with any laws, regulations, codes, or standards.