Short answer: Make sure any fire is out and everyone is safe, leave the gas and power to the cooking line off, and don't cook under that hood again until a trained technician has inspected, recharged and reset the system. Clean the agent off the hood and appliances within 24 hours using warm water and detergent while wearing rubber gloves, and keep records of everything for your fire department and insurer.
What Just Happened
A kitchen hood system like the ANSUL R-102 fires when a fusible link in the hood melts from heat or when someone pulls the manual pull station. The tank pushes wet chemical agent through the piping and out of nozzles aimed at the plenum, the duct and each appliance. On hot grease, the agent forms a foam layer that helps keep the fire from reigniting. Pyro-Chem, Amerex, Kidde and other wet chemical systems work in a similar way.
At the same moment, the system is designed to shut off fuel or electric power to the cooking equipment under the hood. Under the International Fire Code, that shutoff must be reset manually. Gas won't come back on by itself, and it shouldn't.
The First Hour: Safety
- If there was a fire, call 911 and get people out, even if the fire looks out. Fires can spread into the duct.
- Don't fight a grease fire with the wrong extinguisher. ANSUL's owner's guide warns against using ABC dry chemical, CO2 or water extinguishers on burning cooking oil. The placard by your Class K extinguisher says to actuate the hood system before using the extinguisher.
- Leave the gas and power off at the appliances the system shut down. Don't try to reset the system yourself.
- Ventilate the area and keep staff away from the cooking line until it's been cleaned.
- Keep agent off skin and out of eyes. Put on rubber gloves before you touch anything that was sprayed.
Is the Agent Dangerous?
Check the Safety Data Sheet (SDS) for your system's agent. That's the manufacturer's document for first aid, protective equipment and handling, and the servicing company can get you a copy. As one example, the SDS for ANSULEX LPH R-102 Liquid Agent (Tyco Fire Protection Products, revised February 2022) says the product is not classified as hazardous under OSHA's 2012 Hazard Communication Standard. It lists a pH of 7.7 to 8.7, which is mildly alkaline, and potassium acetate as an ingredient.
The same SDS still says to avoid contact with skin and eyes and recommends tight-sealing goggles and protective gloves. Its first aid steps are:
- Eyes: rinse with plenty of water for at least 15 minutes, lifting the eyelids, and consult a physician.
- Skin: wash with soap and water, and get medical attention if irritation develops and persists.
- Inhalation: move to fresh air, and get medical attention if symptoms occur.
- Swallowed: rinse the mouth, don't induce vomiting without medical advice, and call poison control or a physician right away.
Other brands use different formulations. Amerex, for example, describes its KP agent as potassium-acetate based. Don't assume one SDS covers your system. Read the one for the agent in your tank.
Don't Cook Under an Impaired Hood
Once it has discharged, your system can't protect the cooking line. The tank is empty, the detection line has a melted or released link, and the nozzles may be clogged with agent and grease. The IFC requires the system to be serviced after any activation, and the ANSUL owner's guide says to have the system inspected and recharged immediately after a discharge.
That means no cooking on the protected appliances until the system is back in service. That includes gas appliances that share the hood but aren't directly protected. Some fire departments have rules for impaired fire protection systems. The St. Louis Fire Department, for example, publishes fire-watch requirements under its 2018 IFC. Call your fire department or district and ask what applies to you. The St. Louis City page explains who enforces the fire code there.
Get the System Recharged and Reset
ANSUL's guidance is to call a distributor it has trained, have the system inspected and recharged, and have the cause of the actuation determined. Other manufacturers restrict service in a similar way, so ask any provider whether its technician is trained on your brand. A recharge visit usually includes:
- Refilling or replacing the agent tank and replacing spent cartridges
- Replacing the fusible links in the detection line
- Cleaning or flushing the distribution piping and cleaning and recapping the nozzles
- Finding out what triggered the discharge, whether a fire, a pull station, or a component failure
- Resetting the system, then testing the gas or electric shutoff and its manual reset
- A new service tag and a written report
If you don't have a service company, send a request and say the system has discharged. With your consent, we'll pass it to an independent provider who serves your area. The fire suppression recharge and repair page covers the service in detail, and the ANSUL system service page covers R-102 and PIRANHA systems specifically. For what affects the bill, see what restaurant fire suppression costs.
Cleanup: Within 24 Hours
ANSUL's owner's guide says to clean the area within 24 hours of a discharge, using warm water and detergent and wearing rubber gloves. Then rinse and dry everything thoroughly before re-energizing the appliances.
- Wipe down hood surfaces, filters, appliances, prep tables and the floor.
- Throw out food that was open on the line or near the hood. Ask your health department if you're unsure.
- Rinse and dry thoroughly. Don't turn appliances back on while they're still wet.
- If there was an actual fire, ask whether the hood and duct need professional cleaning before you cook again.
Keep cleaning chemicals off the new fusible links and detection cables. ANSUL warns against corrosive or high-alkaline cleaners on those parts.
Who to Notify
- Fire department or district: if firefighters responded, ask whether they need anything from you before you reopen. Some departments want the new inspection certificate. The IFC requires one to be forwarded to the fire code official after an inspection.
- Your insurer: many policies require prompt notice of a loss. Check your policy and call your agent, especially if there was fire damage.
- Health department: after a kitchen fire, the health department may want to inspect. After the June 2025 fire at a Glen Carbon Hardee's, the fire chief said the health department would inspect the restaurant and its hood system. See our Metro East Illinois page for how the Illinois side handles hood work.
- Your landlord or property manager, if the lease requires it.
Document Everything
| Record | Why keep it |
|---|---|
| Date, time, and what staff saw | Helps the technician find the cause and supports an insurance claim. |
| Photos before and after cleanup | Shows the extent of the discharge and any fire damage. |
| Technician's service report and new tag | Proves the system was recharged and tested after activation. |
| Invoices for recharge, repair and cleaning | Needed for insurance and your maintenance file. |
| Hood cleaning certificate (if cleaned) | Shows the exhaust system was cleaned after a fire. |
Before You Reopen
- The system has been recharged, reset and tagged by the technician.
- Gas and electric shutoffs have been tested and manually reset.
- Every appliance is back in its design position under its nozzles.
- Filters are in place, and the hood is clean and dry.
- Any Class K extinguisher that was used has been serviced or replaced. See our Class K extinguisher guide.
- Your fire department, insurer and health department have what they asked for.
If the discharge was accidental, ask the technician what caused it. A pull station in a busy walkway or a damaged detection line can set off the system again. Our restaurant fire inspection checklist covers the everyday checks that help prevent it.
Sources: ANSUL R-102 Owner's Guide (P/N 418127); SDS, ANSULEX LPH R-102 Liquid Agent (rev. Feb. 2022); 2015 IFC ยง904.12 (City of Lawrence, KS); Thornton (CO) FD commercial cooking suppression requirements (2021 IFC); Amerex, What Is a Class K Fire?; Amerex KP system; St. Louis Fire Department, Fire Watch Requirements; EdGlen Today, Hardee's Glen Carbon fire (June 2025). Requirements vary by jurisdiction; confirm with your local fire official.