Locations and Associated Hazards
Now, let's look at the difference between the air handling units that can be found inside the building and those you can find on the roof.
The units inside a building will be found anywhere that they can be hidden. In many buildings you will find them in dedicated equipment rooms and the units will be mounted on the floor. In an equal number of buildings, you will find the units hanging above a corridor or above the space they serve.
The fact that these units are hanging creates a huge danger for firefighters. Typically, these units are hung with unprotected threaded rods, which will fail quickly when exposed to fire conditions. Usually these units use hot water as a heating medium therefore a gas burner is generally not an issue.
Rooftop units pose two specific and different dangers to firefighters. The units are mounted on curbs on the roof, and in most cases the building structure around these units was designed to withstand their weight. Sometimes these units are installed on existing buildings with little regard for the increased load on the roof. Either way the danger of these units falling through the roof is very real. Many of today's buildings use lightweight construction so the roof structure itself can fail in a very short period of time, so if the roof structure fails a unit weighting several thousand pounds will be coming with it.
If no regard has been given to the structure of the building when the unit was installed, there are even greater chances that any substantial increase in heat may lead to failure of the roof structure and the unit falling on firefighters working in the building. Some units are powered natural gas or propane, and these hazards should not be treated any differently then we do every other time.
Exhaust Fans in HVAC Systems
Exhaust fans can be very helpful in our ventilation practices. When used properly they can remove the hot gases of combustion from the spaces we are working in. If we are to use the buildings exhaust fans to assist us in this process we need to know where they are located and how they operate. It's also vital to know what areas they serve and how big they are. If you do not know these facts, I would suggest performing ventilation in traditional methods.
HVAC systems are integral parts of a building, but they can help us and hurt us. The next article will discuss boilers, chillers, and condensers and how they will affect us during firefighting operations. Please take the time to learn about these systems in the commercial buildings you serve, you may find that having this information will make a big difference in outcome of a fire.
MATTHEW STIENE, a Firehouse.com Contributing Editor, is a senior facilities manager for Mecklenburg County, NC, and a firefighter with Robinson Volunteer Fire and Rescue, in Charlotte. He is a licensed professional engineer in North Carolina, New York and Pennsylvania, and is a certified facility management professional. To read Matthew's complete biography and his archived articles, click here. You can reach Matthew by e-mail at firstname.lastname@example.org.