Why Kitchen Exhaust Cleaning and Inspection Matter
Kitchen exhaust cleaning and inspection remove the grease that condenses on the inside of hoods, ducts and exhaust fans before it becomes fuel. Grease filters catch much of the grease in the airstream, but not all of it, and what gets past them coats every surface downstream.
A fire that starts on a fryer or broiler can be drawn into the hood. If the plenum, duct and fan are clean, the fire-extinguishing system has a manageable job. If they are lined with grease, the fire can travel up the duct, through concealed spaces and onto the roof, where it is hard for firefighters to reach.
NFPA 96 places responsibility for inspection and cleaning on the owner or operator. Fire marshals and insurance carriers check the records, and a missed cleaning can affect both a fire inspection and an insurance claim. The rest of this guide explains what proper service involves and how to tell good work from a quick wipe.
NFPA 96 Inspection Frequency by Cooking Volume
NFPA 96 ties the frequency of exhaust system inspection for grease buildup to the type and volume of cooking. The heavier and longer the cooking, the more often the system must be checked. The intervals below are the commonly referenced values. Confirm them against the edition adopted locally, because the AHJ may require more frequent service.
| Type or volume of cooking | Inspection frequency (commonly referenced) |
|---|---|
| Systems serving solid-fuel cooking operations | Monthly |
| High-volume cooking, such as 24-hour cooking, charbroiling or wok cooking | Quarterly |
| Moderate-volume cooking operations | Semiannually |
| Low-volume cooking, such as churches, day camps, seasonal businesses or senior centers | Annually |
These are inspection intervals. The system is cleaned when inspection finds grease buildup, which on many high-volume lines means cleaning at every inspection. A moderate-volume restaurant that adds a charbroiler or extends to late-night hours may move into a more frequent category, so revisit the schedule whenever the menu or hours change.
Signs you need service sooner
- Grease dripping from the hood edge or filters.
- Grease pooling around the rooftop fan or staining the roof.
- Smoke spilling from a hood that used to capture well.
- Fan noise, vibration or a visible grease coating on the fan wheel.
What Cleaning to Bare Metal Means
Cleaning to bare metal means removing grease from every surface of the exhaust system until the original metal is visible, not just reducing the deposit. NFPA 96 uses this as the standard for a completed cleaning, and it applies to the hood plenum, the grease duct, the fan and any components in between.
A cleaning crew typically works through the system in this order:
- Cover appliances and protect the area with plastic sheeting and a containment funnel under the hood.
- Remove the filters for washing or soaking.
- Protect the fire-extinguishing system nozzles, detectors and electrical components without disabling the system.
- Scrape heavy deposits from the hood plenum and duct.
- Apply degreaser and pressure wash with hot water, working from the fan down toward the hood or from the hood up, depending on the system layout.
- Open the hinged fan and clean the wheel, housing and curb.
- Rinse, collect and dispose of wastewater and grease according to local rules.
- Reinstall filters, restore the suppression system to normal and test the fan.
Areas that cannot be reached must be listed on the service report. A crew that cleans only what can be seen from the hood, without opening access panels or the fan, has not cleaned the system.
Access Panels and the Hinged Exhaust Fan
An exhaust system can only be cleaned where it can be reached. NFPA 96 requires access openings in grease ducts so every section can be inspected and cleaned, and those openings are the single biggest factor in how thorough a cleaning can be.
Grease duct access panels
- Located at changes in direction and along horizontal runs at intervals that allow full cleaning.
- Grease-tight, with gaskets and fasteners suitable for the temperature and grease exposure.
- Fire-rated where the duct is inside a rated shaft or wrapped with a listed fire-rated wrap.
- Reachable from the kitchen or ceiling space without cutting finishes. A panel hidden above a hard ceiling is an inspection failure waiting to happen.
Hinged upblast fans
Most restaurant exhaust fans are upblast units on a roof curb. A hinge kit lets the cleaner tilt the fan back on its hinge to reach the fan wheel and the top of the duct, and a restraint (cable or chain) holds it in the open position. Without a hinge, the fan has to be unbolted and lifted, which is unsafe and often skipped. A fan with no hinge, no grease containment device, or wiring too short to allow it to tilt open should be corrected before the next cleaning. Our commercial kitchen exhaust fan page covers fan options and retrofits.
Service Labels, Reports and Record Keeping
After each cleaning, the contractor should post a label at the hood showing the cleaning date, the name of the servicing company and any areas that were not cleaned. Fire inspectors look for this label first, and NFPA 96 calls for it.
The label is not the whole record. A professional service also leaves a written report, and the owner should keep a file of them. A useful report includes:
| Report item | What to look for |
|---|---|
| Date and crew | Company name, technician names, start and finish time |
| Scope cleaned | Hood, plenum, filters, each duct section, fan, roof containment |
| Areas not cleaned | Location and reason (no access, unsafe, blocked panel) |
| Before and after photos | Same locations, showing bare metal after cleaning |
| Deficiencies found | Missing access panels, damaged filters, fan without hinge, roof grease damage, leaking duct |
| Recommended frequency | Based on grease found, compared with the current schedule |
Keep the fire-extinguishing system service records in the same file. Inspectors often review exhaust cleaning and suppression service together.
How to Choose a Kitchen Exhaust Cleaning Contractor
The right exhaust cleaning contractor cleans the whole system to bare metal, documents what they did and could not do, and tells you about deficiencies instead of hiding them. NFPA 96 calls for cleaning by a properly trained, qualified and certified company or person acceptable to the AHJ, so ask your fire marshal what they accept.
Questions to ask before hiring
- What training or certification do your technicians hold, and does the local fire marshal recognize it?
- Do you carry general liability insurance that covers this work, and can you provide a certificate?
- Will you open every access panel and the fan on each visit?
- Do you provide before and after photos and a written report, not just a sticker?
- How do you protect the fire suppression system and handle wastewater?
- Who reports deficiencies such as missing access panels or a fan without a hinge?
Be wary of pricing that seems far below other bids for the same system. The difference usually shows up as unopened panels, a fan left greasy, or no photos. A follow-up check by a second party once in a while is a reasonable way to confirm quality.
If an inspection uncovers system problems such as inaccessible duct or failing fan curbs, our hood service and maintenance team can correct the equipment so future cleanings can be done properly.
Daily and Weekly Tasks for Kitchen Operators
Professional cleaning handles the duct and fan, but the kitchen staff controls how fast grease reaches them. Consistent daily and weekly care keeps filters working, extends the time between professional cleanings and makes inspection results more predictable.
| Frequency | Task |
|---|---|
| Daily | Wipe hood interior and exterior surfaces within reach |
| Daily | Empty and clean grease cups, troughs and drain containers |
| Daily | Confirm all filters are installed, seated and undamaged |
| Daily (heavy cooking) or weekly (light cooking) | Remove and wash baffle filters in a sink or dish machine suitable for them |
| Weekly | Check that the manual pull station is visible and unobstructed |
| Weekly | Look and listen for changes in fan noise, vibration or capture |
| Weekly | Check that a Class K extinguisher is in place and charged |
What staff should never do
- Run the line with filters missing or replaced by mesh or foil.
- Hang utensils or towels from suppression piping or nozzles.
- Move or add appliances under the hood without checking suppression coverage.
- Switch off the exhaust fan during cooking to cut noise or energy.
When the kitchen grows, revisit both the cleaning frequency and the system itself. A hood sized for the original menu may not keep up with a new charbroiler, and our NFPA 96 requirements guide explains the rules that apply when equipment changes.
Exhaust Cleaning and Inspection Questions
- How often does a restaurant hood need to be cleaned?
- NFPA 96 sets inspection frequency by cooking volume: commonly monthly for solid fuel, quarterly for high-volume cooking such as charbroiling or wok cooking, semiannually for moderate volume, and annually for low-volume operations. The system is cleaned whenever inspection finds grease buildup. Confirm the intervals with your local fire marshal.
- Does cleaning the hood filters count as exhaust cleaning?
- No. Filter washing is a daily or weekly task for kitchen staff. Exhaust cleaning covers the hood plenum behind the filters, the full length of grease duct and the exhaust fan, and it must remove grease down to bare metal. Only a trained cleaning company should do that work.
- What does the sticker on my hood mean?
- The service label shows when the exhaust system was last cleaned, which company did it, and any areas that were not cleaned. Fire inspectors check it during visits. If the label lists areas not cleaned, ask the contractor why and get the access problem fixed before the next service.
- Why does my cleaning contractor say the fan needs a hinge kit?
- A hinge kit lets the cleaner tilt the upblast fan open to clean the wheel, housing and top of the duct safely. Without it, the fan must be unbolted and lifted, which is often skipped. NFPA 96 calls for fan access for cleaning, and a hinge is the common way to provide it.
- Can my staff clean the exhaust duct themselves?
- NFPA 96 calls for exhaust system cleaning by a properly trained, qualified and certified company or person acceptable to the AHJ. In practice that means a professional cleaning contractor. Staff should handle daily and weekly hood surface and filter care, not the duct or fan.
- What happens if grease is found in a duct I cannot reach?
- The contractor should list the area as not cleaned on the label and report. The fix is usually adding listed access panels or correcting a duct route so the section can be reached. Leaving it in place means that part of the system keeps accumulating grease between visits.