Arson Unit has a Burning Desire to Solve Fire Crimes

December 30, 2025

Arson Unit has a Burning Desire
to Solve Fire Crimes

by Laura L. Sullivan, Public Relations Specialist

How do you investigate something that consumes the evidence of a crime? Not only will a fire often burn up whatever started it – whether that is a faulty power outlet or a deliberate accelerant – but putting out the fire with hundreds of gallons of water can also destroy crucial evidence. Sergeant Jennifer Cox and other members of the Arson Unit fight against difficult odds to discover the cause of suspicious fires.

“I’m a fire geek,” Sergeant Cox said. “I love trying to figure out the puzzle.” With a decade of experience as an arson investigator, she has seen a wide variety of fires. The Arson Unit doesn’t investigate every conflagration. They will be called out if there is an injury to an occupant or a firefighter, for property damage over $1-million, or for any fire deemed suspicious or criminal in nature. Other fires may be examined by an investigator with a fire department, or one from an insurance company.

“Any time we go out to a fire, the biggest thing is to try to find the Area of Origin.” This is the place where the fire initially ignited, and can often be determined by analyzing burn patterns and the intensity of damage. This can help an investigator determine the cause of the fire, which can show if it was accidental or deliberate. Fires can be classified as natural, incendiary, or undetermined. An example of a natural fire could be a lightning strike. An incendiary fire was initiated by a human, whether it was accidental or intentional. “You could put your fireworks in your garbage after the Fourth of July and if a fire starts it is incendiary, but accidental.”

Plenty of fires are accidental but preventable. Smoking, careless use of candles, and lithium batteries start many fires that could have been avoided. Spontaneous human combustion is a myth, but fires can sometimes start from unexpected sources with no spark or flame. Linseed oil, which is used on wood and in varnishes and stains, has an exothermic reaction as it dries, generating enough heat to ignite a rag. Some glues can have a similar reaction. A home improvement project can turn into a blaze if you’re not careful.

“Part of our job is the scientific method,” Sergeant Cox said. “We have to go through the steps – finding a hypothesis, testing the hypothesis, and if that doesn’t provide a solution we have to go back to the drawing board.” She has to understand how fire starts, grows, and moves, how it reacts with different combustible materials like wood or synthetics, and how it is affected by the presence or absence of oxygen. An investigation is systematic, starting with a perimeter and exterior examination before moving inside. Once inside they frequently have to dig and sift through entire rooms full of devastation looking for any clue of the fire’s origins. “You’re not going to find a matchstick, but you might find a melted lighter,” Sergeant Cox said.

There might be areas where they suspect an accelerant could be lurking, and a sample can be sent to the lab for testing. One problem with finding an accelerant is that most tests look for petroleum products, and the majority of our household items contain some sort of petroleum product – essentially, plastics and synthetic fibers. Everything from carpets to cabinets to clothes can contain petroleum-based material. Ideally an investigator will take a comparison sample from an unburned section too so they can have a baseline for the chemical composition.

In addition to physical evidence, they conduct an investigation that involves interviewing witnesses and checking any video evidence. “Witness statements from the people who first see the fire can give our biggest clues,” said Sergeant Cox. “What color was the smoke, where did you see smoke or flames? Different materials make different color smoke.” If they say it started out white and then became black, maybe that means the fire started in the attic, where most of the material is natural, like wood, and then spread to where there are synthetic fibers like curtains and sofas.

An investigator has to consider all possible clues. Is the resident a smoker? Is the house paid for? Is it insured? What appliance did they have plugged in?

All fires behave a little differently. She recently worked a fire in a hoarder’s house, and there was so much fuel that the entire room burned, floor to ceiling, making it much harder to find evidence that might point to a cause. If they’re lucky, they have a fire that exhausts itself quickly because of a lack of oxygen.

The four arson investigators take turns being on call for a week at a time. Last year they investigated 31 fires. Five of them were deemed to be arson. One of the hardest cases Sergeant Cox ever worked was the fire at the Alligator Wildlife Discovery Center in Madeira Beach that killed dozens of animals. One of the most satisfying was a case where an employee torched the home that their boss had just purchased. All too often, proof of arson comes down to tiny fragments of evidence in danger of being destroyed, but in this case the suspect had been caught on video so it was relatively easy to find out who they were and make an arrest.

Whether through an accident or foul play, a fire can spread through a house in minutes. Read the next story for information on what to do if there’s ever a fire in your home.

What to Do if You Have a House Fire

by Laura L. Sullivan, Public Relations Specialist

If there’s a fire in your house, you may only have a few minutes to save your life. Sergeant Jennifer Cox of the Arson Unit has some advice about what to do if you ever find yourself in that situation.

Perhaps the most frightening scenario is if a fire starts overnight while you’re sleeping. If you become aware of a fire as you wake up, resist the urge to jump to your feet. “We get people who unfortunately perish in fires because they wake up, and their first instinct is to get up. When they stand up they breathe in the hot gases.” Instead they should get low. “A low crawl will keep you below the smoke and hot toxic gases.” Stay low and get out. In an intense fire the temperature might be 100 degrees Fahrenheit at floor level but 600 degrees Fahrenheit at eye level. Burning household items can also create poisonous fumes.

You should sleep with your bedroom doors closed to buy extra time in the event of a fire. “Opening a door can alter a fire in an instant,” Sergeant Cox said. She has seen cases where a fire in one room suddenly spread unchecked through the entire house when someone opened the door. “The occupant opened the door to try to fight it and then gave up and left, but they didn’t close the door behind them. If they had closed the door the fire might have been contained in that room or spread more slowly.”

As soon as you are aware of a fire, alert anyone else in the house. If you can safely get them out, do so. Don’t stop to save any of your possessions. Every fire is different, and there are many variables, but it may be that you have to leave people or pets inside while you save yourself. As soon as the fire department arrives, let them know what people and animals are in the house and where you think they are. Firefighters have the equipment to survive in conditions where you could not, and will have a better chance of saving anyone inside. Once you are out, never reenter a burning building.

If the fire is outside of your room, check to see if the door or doorknob are warm before opening the door. If your route is blocked by fire or smoke, keep the door closed and escape through a window if possible. If you can’t escape, call 911 and then try to seal any cracks under the door with a wet towel. Signal for help at the window.

You probably remember this advice from elementary school: if your clothes catch fire, immediately stop, drop to the ground and cover your face, and roll until the flames are out. This deprives the fire of the oxygen it needs to continue. However, if you run, you’re only giving the fire more oxygen.

Should you try to put a fire out yourself? Again, that depends on a lot of variables. “A lot of people don’t keep fire extinguishers in their home,” Sergeant Cox said. If there is a small fire on the kitchen stove, you may be able to put it out with a fire extinguisher, or smother it with a fire blanket. But if you aren’t immediately successful, or have any doubt about being able to put it out, get everyone outside and call 911.

You and your family should have a fire plan in place. Make sure everyone knows at least two ways to escape from every room. Talk with them about how important it is to get out fast. A small fire can turn into a major fire in seconds, and even away from the flames the air can get unsurvivably hot. Smoke will make the room dark as night, and the gases are poisonous. The most important thing is to get out quickly.

Smoke alarms give an early warning that increases your chance of surviving a fire. Make sure there are smoke alarms on every floor, including the attic, basement, and garage. Some alarms come with a 10-year battery, but if yours doesn’t, change the batteries twice a year. Many people make a note to do this when Daylight Savings Time begins or ends.

Take steps to keep fires from starting in the first place. Never leave candles or heaters near anything flammable, and don’t leave the kitchen unattended when you’re cooking. Be careful of home improvement projects that involve electricity, since installing something wrong can lead to fires later. Keep flammable material away from outlets and extension cords.

Florida presents a special fire challenge when hurricanes bring flooding. “We had people after the hurricane who didn’t get their wiring redone and they had fires after the power was turned back on,” Sergeant Cox said. Golf carts, electric cars, and even lawn equipment can be fire hazards after a storm, because when lithium batteries are exposed to saltwater they can burst into flames hours or days later. Even without saltwater damage, lithium batteries can start fires when they are overcharged.

Technology, such as smoke alarms, and increased education can keep you safer from fires, but when fires do start it seems that modern houses burn faster than “vintage” houses. Older houses had more solid, natural materials, and though wood is certainly flammable, a heavy wooden piece is harder to ignite and burns more slowly than sofa made of synthetic fibers. Modern wall and floor materials also ignite more easily and burn more quickly. A trend for open floor plans instead of many separated rooms ensures that fires get plenty of oxygen and can move more easily throughout the house.

Take the steps you can to prevent a fire from starting in your home. But if it ever does, remember that your life is far more valuable than your property, and get out fast.