Solar panels should always be considered charged with electrical current.
A ventilation opening on a peaked roof should be at the top of the peak on the leeward side away from the wind. Firefighters assigned to the roof must be competent, resourceful and constantly aware of changing conditions.
The roof of the fire building is a critical area at a structure fire. It is important that the firefighters assigned to the roof are competent, resourceful and constantly aware of changing conditions. They should initiate a thought process at the receipt of an alarm, while enroute to the scene and throughout the incident.
If the rear of the fire building is visible to firefighters as they approach the scene, they should memorize the various facets at that location, then the sides and continue as the front of the building is viewed. Window locations, doors, building height, fire escapes, adjoining buildings, construction (especially the roof) and smoke conditions should be noted. They should concentrate on factors that can affect life safety or fire department operations. Where is the fire located? Where is it going?
Predictions should include the best location for venting the fire building. Since the firefighters assigned to the roof will be concerned with the ventilation of the upper parts of the fire building, it must be decided how to get onto the roof. Should an aerial device, portable ladders, fire escapes or adjoining building roofs be used? Which will offer the fastest and safest means?
Observation continues as the firefighters ascend to the roof. Can they further pinpoint the location of the fire? Is anyone on fire escapes or at windows awaiting rescue? Once firefighters are on the roof, it must be ascertained whether the roof is sound and what material does it consist of: concrete, lightweight wood, heavy timber, steel bar-joist?
Air and light shafts may be completely enclosed and not visible from ground level. Adjoining buildings may share the same airshaft. Can the windows within the shaft be used for ventilation? Is fire visible from them? If so, then notifying the interior units of fire at this location can assist them in their fire attack. The view from the roof may indicate that heavy fire coming from these windows has spread to the adjacent buildings.
Size-Up on the Roof
Since the roof can be an excellent platform for size-up, the information gathered there can assist the incident commander in his or her decision making. Firefighters on the roof can typically observe:
• That the overall size of the structure may be easier to determine from the roof
• A complete view of the surrounding buildings and exposures
• The presence of firewalls that separate the attic or cockloft below the roof and which parapets above the roof line act as fire stops by preventing a surface fire from involving the entire roof
• A breakdown in the firewall that could indicate deficiencies below the roof line that could allow a fire to spread through the firewall to adjacent areas or other buildings
• Occupants trapped on fire escapes at the rear or side of a building out of the view of the incident commander
• Fully enclosed light or airshafts contained within a building and if people are observed trapped at these locations
• If anyone has jumped and is lying on the ground on the rear or sides of the fire building, within an air or light shaft, or on a lower roof in need of rescue
• Smoke conditions from any openings that exist in the roof; these include skylights or stairways that access the roof from the interior
• The cockloft and attic spaces can also be closely observed for the presence of fire and smoke.
• The amount of smoke and/or fire emitting from roof ventilators, either on the rooftop or side of the building
• The presence of a courtyard and access points that are not readily visible from ground level; in some instances, the courtyard may have access only through the building’s interior
• The presence of a penthouse on the roof indicating the existence of an elevator in the building
• An unsupported parapet wall on the front of the building can be closely observed for stability
• Large air conditioners, signs, billboards or other heavy dead loads on the roof
• Fire may already involve parts of the roof structure; the location, intensity and involvement can be key information for the incident commander
• That conditions found on the roof may conflict with reports being given from the interior sectors (this can occur due to limited visibility of those operating on the interior to get the big picture in relation to the overall situation; units operating on the roof often have a distinct advantage in determining the full scope of the situation)
• Keep command informed of conditions that indicate problems not visible from the command post or from the interior
• Report the problems observed; estimate the threat to the occupants, firefighters, fire building and adjoining structures; this report should include recommendations on fire control or rescue.
Size-up accomplishes problem identification. This permits us to determine the strategy, tactics and tasks that are needed to address the problems found. Typically, a critical strategy at a working structure is ventilation. Ventilation is performed to assist firefighters in achieving life safety and fire control. It is accomplished by removing the pent-up heat and gases from the occupied and concealed areas of the building.
Roof, or vertical, ventilation is just one method of ventilation that can be used. Vertical ventilation can be achieved by opening skylights, bulkhead doors or scuttle covers or by placing holes in the roof. By creating these roof openings, we can prevent a buildup of heat and fire on the top floor of a structure, in an attic or cockloft. Deadly smoke and fire can be drawn to the exterior, clearing stairways and letting trapped occupants escape while creating a safer and more visible route for firefighters to enter and fight the fire.
By opening the roof, we vent the heat and fire to the exterior. In many cases, we are increasing the fire’s intensity by providing air that fuels the fire, but channeling the heat and smoke to where we want it and stopping or minimizing fire spread to other areas while interior units attack and extinguish the fire with hoselines.
Opening the Roof
Roof ventilation should be in conjunction with horizontal ventilation on the upper floors. The opening of a roof directly over the fire area vents the fire to the exterior. The opening of the roof away from the fire will draw the fire to that opening. Improper ventilation can endanger civilians and hoseline crews by pulling the fire onto them as well as causing the fire to spread.
The experience of the firefighters assigned to the roof is important. They must draw on their knowledge and expertise to perform their duties. They must ascertain whether the roof is safe and be prepared to abandon roof operations if unsafe conditions exist. When a roof is no longer safe, it can affect the overall operation. The incident commander must decide whether the mode of attack should be changed from an offensive to a defensive attack.
New firefighters should not normally be the first to ascend to the roof. Their concentration may be totally consumed with venting the roof, causing them to miss danger signs. Constant size-up is needed to detect changing conditions.
Firefighters operating on roofs should work in pairs. When ordered to open the roof, they must determine an appropriate location. This determination will be aided by their observations of the building and the location of the fire prior to reaching the roof. Visual indicators on the roof can assist in determining where to place the vent hole. Fire burning through the roof, bubbling tar, melted snow on a snow-covered roof or dry spots on a wet roof can assist in locating the fire below.
The wind should be at the firefighters’ backs and they should make one large hole, not a few small holes. A ventilation hole should be four feet by four feet on a small roof and at least eight feet by 12 feet on a large roof. Naturally, this depends on the size of the structure.
Openings should end at the roof rafters. Rafters can be used as a guide for a straight cut and ensure stability for the firefighters operating around the opening. After all of the saw cuts are completed, the roofing material should be pulled back onto the roof to clear the opening. A tool should then be used to probe the opening, pushing down any ceiling or obstructions that could restrict ventilation.
Be prepared to encounter more than one ceiling. It is virtually impossible to see into the opening due to the heat and smoke being vented; thus, our tool must be our eyes. If a second ceiling is encountered, push it down and probe for the possibility of a third ceiling. Experience will teach us when a vent hole is effective by the amount of smoke and gases being expelled. The units operating inside the structure should be notified when the opening is completed. They will be able to advance their lines into the area using the opening to vent their approach.
Problems Delaying Or Preventing Rooftop Ventilation
There may be problems that delay or prevent the opening of the roof. This could involve:
• Mechanical problems with the saw
• The saw blade may need to be changed for the type of roofing material being encountered
• A very steep roof that slows down the overall operation while ladders are positioned and the roof is opened
• Heavy smoke conditions slowing down operations
• Heavy fire conditions requiring hose-lines to let the firefighters operate on the roof
• An untenable situation caused by fire conditions
• A weak or spongy roof, which is deemed unsafe to operate on; this can be found by firefighters when first mounting the roof, or conditions can deteriorate while they are working on the roof
• A roof that has had another roof built over it, sometimes referred to as a double roof
• A buildup of snow or ice on a roof that must be removed
• A buildup of water due to clogged roof drains that must be opened
• Weakened roof boards on a vacant building that slows the firefighters in order to ensure safe operations
Improper Roof Openings
By placing a ventilation hole in the roof, we pull the fire to that location. If the ventilation hole is in the wrong location, the fire area will increase in size as uninvolved areas are exposed. This improper action can endanger occupants and hoseline crews fighting the fire.
An opening made on the lower part of a peaked roof and not at the peak of the roof can provide inadequate ventilation. On one occasion, a fire had burned through the lower part of a peaked roof near where the roof sits on the outside walls. It was reported to the interior sectors that the roof had been opened. A top-floor fire was attacked and the visible fire had been knocked down. As firefighters prepared to enter the fire area, it flashed over with the resounding bang of a backdraft. The firefighters quickly regrouped and knocked the fire down again.
This time, the firefighters waited and again the fire flared up with a similar explosive sound accompanied by the room again flashing over. The truck company on reaching the roof reported that the roof was burned through, but in a lower area that was inadequate for ventilation purposes. The truck company placed a correct vent hole and the fire was quickly handled. (In this case, the superheated gases had accumulated in the attic space above where the fire had burned through the roof. Part of the ceiling of the fire room had failed and the room was open into the attic. The amount of smoke coming from the roof opening gave the false impression that the roof was vented. Though burned through, the opening was not at the correct location for proper ventilation. As the visible fire was knocked down in the room, the superheated gases in the upper area of the attic continued to re-ignite the fire. Without the topside ventilation, a backdraft type of situation was created.)
Rooftop Solar Panels
The movement toward “green energy” includes the installation of thermal and photovoltaic (PV) rooftop systems for capturing sunlight (see photo above). The thermal systems use sunlight for heating of liquids to use for hot tap water, hot-water heat or swimming pools, while PV systems turn it into electricity. Firefighters need to identify the systems that are present on a structure. The greatest hazards are with the PV systems since they are always on during daylight and cannot be shut off.
Tripping and slipping are the most common types of hazards for firefighters on rooftops with solar panels. Firefighters must consider the additional weight imposed on the roof by the solar panels, especially if fire has attacked the roof supports and weakened them. The presence of PV panels can impair rooftop ventilation tactics by preventing the roof from being opened for ventilation at the optimum location. Realize that the panels should never be damaged or compromised to perform vertical ventilation. Do not break, remove or walk on PV modules because of the inherent electrical hazard.
Another hazard is the potential flame-spread characteristics of the modules should a fire burn upward through the roof from below or from an exposed building fire. The panel materials do not necessarily have good fire-resistant characteristics, and they can produce toxic fumes when burning. Should PV panels become involved in fire, treat them as you would any energized electrical equipment in that electric shock possibilities are constant.
Though most other types of energized electrical equipment can be shut down, a solar panel exposed to sunlight is always on and energized. This can create problems for firefighters when shutting down the electricity to a structure and can be a dangerous source of electric shock, or it may initiate a rekindle. There is the possibility of residual electricity in these systems that could cause electric shock. Firefighters should at all times treat these systems as though they are energized. This means that panels, conduit or other components can also be energized.
PV modules, if covered with 100% light-blocking materials, will stop electrical generation. Yet, if using salvage covers, they may still permit some sunlight through and allow generation of electricity. Moonlight is reflected light and will not energize the panels, but lightning may generate a temporary surge.
Scene-mounted lighting does not produce enough light to generate an electrical hazard in the PV system. PV systems may contain an optional battery storage system for nighttime use, which could present an electrical shock hazard. The incident commander should request assistance from the local electric utility at any incident where PV panels are present and the power must be shut down.