Overhaul is the phase of firefighting that comes after the main fire has been knocked down. It’s the process of searching for and extinguishing any hidden pockets of fire, smoldering embers, or hot spots that remain inside walls, ceilings, floors, and other concealed spaces. A single overlooked pocket of embers can reignite and cause a full rekindle, so a fire is not considered fully extinguished until overhaul is complete.
Why Overhaul Matters
When a visible fire is brought under control, the danger isn’t over. Fire can travel inside wall cavities, spread along wooden structural members hidden behind drywall, and smolder in insulation for hours. These hidden fires produce no visible flame and little smoke, making them easy to miss. Without a thorough overhaul, a crew could pack up and leave only to get called back when the building reignites.
Overhaul also gives firefighters the chance to assess structural damage, identify weakened floors or ceilings, and begin the transition toward investigation. It’s physically demanding, detail-oriented work that often takes longer than the initial fire attack itself.
How Firefighters Conduct Overhaul
The basic approach is systematic: crews work through burned areas pulling apart walls, ceilings, and floors to expose anything still burning behind them. They look for discoloration, feel for heat, and watch for wisps of smoke that signal hidden fire.
The primary hand tools are pike poles and roof hooks, which have sharp piercing tips designed to punch through drywall and pull it away from studs. Firefighters sometimes reverse the pike pole and use the blunt end when they need a larger striking surface, particularly when punching through ceilings from above on a roof, where the sharp tip can get stuck in wooden attic members and make the work exhausting. Axes, pry bars, and hand saws also get heavy use for opening up walls and flooring.
Thermal imaging cameras have transformed overhaul. These devices detect heat signatures through surfaces, letting firefighters pinpoint exactly where hot spots are hiding before tearing anything apart. Instead of ripping open every wall in a room, a crew can scan with the camera and focus their efforts on the spots that actually need attention. This saves time, reduces unnecessary property damage, and makes the process safer.
The Hidden Toxic Hazard
Overhaul is one of the most chemically hazardous phases of firefighting, partly because it looks deceptively calm. The flames are out, visibility is better, and the urgency drops. That combination leads some firefighters to remove their breathing protection too early.
Research shows that even after flames are knocked down, the overhaul environment contains significant levels of toxic compounds. Airborne cancer-causing chemicals called polycyclic aromatic hydrocarbons (PAHs) reach median concentrations around 512 micrograms per cubic meter during overhaul. Benzene, a known carcinogen, has been measured at about 0.9 parts per million. These levels are far lower than during the initial fire attack, but they’re still substantial, especially for prolonged exposure.
One study exposed mice to overhaul conditions where standard gas meters showed readings well below safety ceiling limits. Despite those “safe” readings, over 3,800 lung genes were expressed differently in the exposed mice compared to controls, indicating real biological harm even when the numbers on the meter look acceptable. This finding highlights a gap between what conventional monitoring catches and what the body actually absorbs.
The physical act of tearing apart walls and ceilings also releases hazards that weren’t created by the fire itself. Older buildings may contain asbestos in insulation, floor tiles, or joint compound, and overhaul activities that disturb these materials send fibers into the air. Firefighters face elevated rates of mesothelioma (a cancer strongly linked to asbestos), as well as higher rates of bladder, prostate, testicular, and colon cancer compared to the general population. Overhaul, along with fire suppression and rescue, is one of the activities most likely to stir up asbestos-containing building materials.
Breathing Protection Standards
The National Fire Protection Association’s standard on firefighter safety (NFPA 1500) treats the overhaul environment as a suspected hazardous atmosphere. Firefighters working in overhaul areas, and on floors above the fire floor, are required to use their self-contained breathing apparatus (SCBA) unless air monitoring confirms the atmosphere is safe and effective ventilation is actively maintaining that safety.
Even when ventilation is running and conditions improve, the standard says firefighters may remove their facepieces only under direct supervision, and their SCBA units should remain on their backs or be immediately available. In practice, compliance varies across departments. The growing body of evidence on cancer risk has pushed many departments toward stricter enforcement and a culture of keeping SCBA on throughout the entire overhaul operation.
After overhaul is finished, contaminated gear becomes its own hazard. Turnout coats and pants absorb carcinogens through soot and smoke residue. NFPA 1851 provides guidelines for cleaning and decontaminating protective equipment after structural firefighting, and ongoing research continues to refine best practices for getting those chemicals out of the fabric before they transfer to the firefighter’s skin.
Protecting the Fire Investigation
Overhaul creates a tension between two goals: making sure the fire is fully out and preserving evidence of how it started. The process of ripping open walls and pulling apart burned materials can destroy fire patterns, char indicators, and other physical evidence that investigators rely on to determine the fire’s origin and cause.
The National Institute of Justice identifies overhaul activities as a direct threat to fire scene evidence through movement, removal, contamination, and destruction of key patterns. For this reason, firefighters are trained to limit excessive overhaul in areas near the suspected point of origin. When arson or suspicious circumstances are possible, crews work more carefully, document what they find, and coordinate with investigators before disturbing certain areas.
In practice, this means overhaul near the seat of the fire proceeds more slowly and methodically. Crews may photograph conditions before pulling materials apart, set aside debris rather than throwing it out windows, and flag anything unusual for the investigator. The goal is to balance complete extinguishment with keeping enough of the scene intact to tell the story of how the fire started.