Planning A Ventilation Operation

By John W. Mittendorf

Of the numerous fireground tasks that you must prioritize on your arrival at a structure fire, you also must consider a multitude of factors, not the least of which should be firefighter safety. In concert with a modern fire environment that is capable of readily flashing over, ventilation should always be a top priority. Therefore, how do you plan your intended ventilation operation?

The first priority in any ventilation operation is to aid in the evacuation of occupants and/or improve the environment and safety of fire suppression personnel. Therefore, plans for ventilation operations should consist of three basic considerations and begin by identifying the direction (horizontal or vertical) smoke, heat, and fire gases must travel to exit a structure:

DIRECTION OF TRAVEL

Horizontal

• Effectiveness is limited and does not take advantage of the natural path of travel of heated gases/smoke.
• Easy and relatively safe. Can often be accomplished from the ground.
• Normally limited to the use of natural openings (i.e. doors and windows).

Vertical

• Can require additional personnel, equipment, and TIME for completion.
• Normally considered the most effective avenue to exhaust contaminants:
  • Heated products of combustion naturally rise upward.
  • The highest concentration of heat is at the top of a room. This is the area that flashovers normally begins.
• Accomplished by using natural construction openings, or cutting an opening.

MOVING CONTAMINANTS
When you have established the direction of travel, then you can select a method for actually moving contaminants:

• Natural. Natural convection relieves accumulations of contaminants. This is normally limited to the prevailing wind and/or the location of the ventilation opening to the contaminated area.
• Pressurized Ventilation. Horsepower is used to augment or overcome natural conditions. Examples are HVAC systems and portable fans, blowers, etc. Currently, the most popular method of pressurized ventilation is positive pressure with gasoline or electric blowers.

TYPE OF OPENINGS
Once you know the direction of travel and the method to move contaminants, you must determine the type of opening to use to achieve the desired result.
Natural Construction Openings

• Natural construction openings (skylights, windows, doors, scuttle covers, etc.) can often provide sufficient ventilation. However, ensure the proper location of these openings in relation to the area to be vented. Additionally,
  • Open doors and windows in conjunction with a prevailing wind.
  • Remove any blinds and shades in windows.
  • Break glass with minimal force.
  • Create openings as close to fire as possible.

  Stairshaft

  • Opening a penthouse/bulkhead door can reduce heat and smoke within a stairshaft and hallways in multistory buildings. This can be a very simple yet effective form of ventilation when the effort expended is considered.

  Over the Fire

  • Cutting a ventilation opening over or near a fire (offensive ventilation-heat hole) can vertically channel a fire and its byproducts. Obviously, this can also be accomplished if considered safe.

  Ahead of a Fire

  • Cutting an opening ahead of a horizontally traveling fire (defensive ventilation-strip ventilation) can control the extension of fire in addition to ventilating heat and contaminants. This can be a time and personnel intensive operation.

  Use the checklist above to plan your ventilation operation at the scene. It is easy to remember and you can use it to quickly determine the feasibility and operational parameters of your intended ventilation operation.

  John W. Mittendorf joined the Los Angeles City (CA) Fire Department (LAFD) in 1963, rising to the rank of captain II, task force commander. In 1981, he was promoted to battalion chief and in the year following became the commander of the In-Service Training Section. In 1993, he retired from LAFD after 30 years of service. Mittendorf has been a member of the National Fire Protection Research Foundation on Engineered Lightweight Construction Technical Advisory Committee. He has provided training programs for the National Fire Academy in Emmitsburg, Maryland; the University of California at Los Angeles; and the British Fire Academy at Morton-in-Marsh, England. He is a member of the editorial advisory board of Fire Engineering and author of the books Truck Company Operations (Fire Engineering, 1998) and Facing the Promotional Interview (Fire Engineering, 2003).