Grease Dripping from Kitchen Exhaust Duct: Causes and Fixes

Grease Dripping

10/8/202611 min read

Grease dripping from kitchen exhaust ductwork isn’t always a sign that the system simply needs another cleaning. A drip can point to grease buildup, a duct joint or layout issue, or another problem that needs assessment. The source may not be obvious from the kitchen, but the mess on surfaces and equipment is immediate.

It’s understandable to worry about fire risk, hygiene, and disruption to service. Keep food-contact surfaces and equipment clear of drips, make the affected area safe, and arrange an assessment rather than guessing at a fix. Cleaning may help, but a repair or ductwork modification could be needed if the issue relates to the duct’s condition or layout.

This guide explains common reasons grease escapes, what to do first, and how to choose a lasting response based on the cause. You’ll also learn when commercial kitchen exhaust A&A and custom-fitted ductwork may be relevant, so you can address the source of the leak rather than only its visible effects.

Key Takeaways

Grease dripping from kitchen exhaust ductwork is a symptom, not a diagnosis. Assess the source before choosing a fix.
Grease deposits, a damaged or poorly sealed joint, and unsuitable duct routing are possible causes.
Cleaning addresses deposits, while repair or modification may be needed for a defect or system-layout issue.
If grease is actively dripping, keep people and food-contact surfaces away, record what you observe, and arrange an assessment.
A system-focused assessment considers the drip location alongside the duct route, hood, and exhaust operation to guide the next step.

Grease dripping from a kitchen exhaust duct: what the symptom means

Grease dripping from a kitchen exhaust duct is the visible escape or collection of grease carried in cooking vapour as it cools and deposits on surfaces inside the exhaust system. A drip is a symptom, not proof of one particular defect. Grease can build up inside the system and become visible at a low point, opening, or joint. The spot where it lands may not be where it first accumulated.

Details can help narrow down the possibilities. Note whether drips occur during busy cooking periods, after the system has cooled, or continuously. Record the cooking activity and whether the pattern changes after maintenance or an exhaust system change. These observations can guide an assessment, but they can’t confirm the cause on their own.

Where can grease appear in a commercial exhaust system?

Cooking vapour passes from the hood through grease filters and into ductwork, then travels towards the exhaust fan. A kitchen exhaust hood captures vapour at its source, while the connected components carry it out of the kitchen. Grease on an exposed hood surface differs from seepage at a duct joint or grease collecting at a low point in the duct.

Trace the visible pattern without opening or dismantling equipment. A drip beneath a joint may draw attention to that area, but grease could have travelled along the duct or collected upstream before escaping. The location is useful evidence, not a diagnosis.

Why should operators take a grease leak seriously?

Grease can contaminate food-contact surfaces and equipment. A leak can also leave floors or work surfaces slippery, create extra cleaning demands, and interrupt kitchen operations. If grease accumulates inside the exhaust system, it adds combustible material and can increase fire risk. Assess the extent and location of the buildup instead of assuming based on a visible drip.

Keep people and food-contact surfaces away from active drips until the area is safe. If grease is near heat, electrical equipment, or an active work area, arrange a prompt professional assessment. Don’t treat wiping away visible grease as a lasting fix: it clears the immediate mess but doesn’t establish where the grease came from or whether it’s still escaping.

Why grease builds up or escapes from kitchen exhaust ductwork

Cooking releases grease-laden vapour that travels from the hood into the duct. As the vapour cools along the route, some grease can settle on internal surfaces instead of reaching the exhaust fan. Over time, deposits may collect around bends, transitions, or low points. If grease later appears outside the duct, a separate issue may also be involved: a compromised joint or damaged duct can let accumulated grease escape.

Accumulation is grease left behind inside the duct as vapour cools; escape is grease passing through a defect or opening in the ductwork. Both can occur together, but a drip alone doesn’t establish the amount of buildup or the condition of a joint. The NFPA 96 Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations provides a reference for commercial cooking ventilation and fire protection.

Grease accumulation, cooling, and condensate

Vapour changes as it moves from the hot cooking area through ductwork with different conditions along its route. Grease can adhere to internal surfaces, then build up where airflow changes direction or the duct narrows or transitions. A visible liquid may include grease mixed with moisture, but appearance alone can’t identify its exact composition or source. Don’t assume a drip is harmless condensation.

Joints, duct condition, and airflow clues

A loose or poorly sealed connection, damaged duct section, or other compromised area may allow grease inside the system to seep out. Weak hood capture, unusual odours, visible smoke, or a noticeable change in airflow are additional clues to record. They warrant assessment, but don’t prove that the exhaust motor or duct design is at fault.

Cooking load and maintenance history also provide useful context. A kitchen that has added equipment, changed its menu, or increased high-grease cooking may place different demands on the exhaust system. Note when the dripping began and whether it follows particular cooking periods or maintenance work. These details can guide a closer look, but they aren’t standalone diagnoses.

If an assessment points to a duct route or system condition that needs to change, commercial exhaust addition and alteration services can help address the underlying layout or installation issue.

Cleaning, duct repair, or modification: which response fits?

The right response depends on the findings. Cleaning targets grease deposits inside the system. Repair addresses a local defect, such as a damaged or poorly sealed connection. Modification addresses a wider issue with the duct route or system layout. For grease dripping from kitchen exhaust ductwork, treating only the visible mess may leave the cause untouched.

ResponseWhat it addressesWhen it may fitCleaningGrease deposits in accessible parts of the exhaust system.Visible buildup or maintenance history suggests deposits need attention.RepairA local defect in a joint or duct section.Inspection identifies a damaged or compromised connection.ModificationA wider issue with duct routing or system configuration.The assessed layout or condition appears to contribute to recurring problems.

When cleaning may be part of the solution

Visible internal deposits and the system’s maintenance history can help determine whether cleaning should be considered. Cleaning may reduce grease buildup, but it won’t restore a damaged joint or correct unsuitable duct routing. If grease returns after cleaning, reassess the system rather than assuming more cleaning alone will solve the leak.

The hood, filters, ductwork, and exhaust fan work as connected parts. For broader context on the hood’s role and how it fits into the system, see this commercial kitchen hood guide.

When duct repair or modification deserves assessment

Recurring drips, visible damage, or signs that grease is escaping at a connection call for closer attention to duct condition. If the issue appears to involve the route or overall layout, commercial kitchen exhaust addition and alteration (A&A) may be appropriate. When modification is indicated, custom-fitted ductwork can be tailored to the project layout. Learn more about commercial kitchen ductwork fabrication.

Choose the response based on the source, not just the symptom. Cleaning can address deposits; a local defect calls for attention to that defect; and a system-layout issue may need a considered modification. A commercial exhaust system assessment helps connect the evidence to the right next step.

What to do when grease starts dripping from the exhaust duct

Take practical steps first, then arrange an assessment. If grease is actively dripping, keep people and food-contact surfaces away from the affected area until it’s safe. Don’t climb to reach ductwork or try to seal or scrape a leak yourself.

Protect the area. Keep staff, customers, and food preparation away from active drips. Address contaminated surfaces according to your kitchen’s hygiene procedures, and treat slippery floors as a hazard.
Record what you observe. Note where the grease appears, when it starts, whether it changes with cooking activity, and whether it returns. Take photographs from a safe position. Don’t touch duct interiors or open panels to investigate.
Review recent changes. Record any recent cleaning, renovation, equipment changes, or shifts in cooking operations. These details may help explain when the symptom began, but they don’t establish its cause.
Arrange an assessment. Share your notes and photographs so the visible drip can be considered alongside the duct route and exhaust system. Broader context on Singapore F&B exhaust requirements is available in this F&B kitchen exhaust requirements guide.

Safe observations to record before assessment

Be specific. For example, note whether grease appears below a joint, near a bend, or on a hood surface, and whether it occurs during particular cooking periods or after the system has stopped. Record when the issue first appeared and whether it has happened before. Photos can show how the visible pattern changes over time, but don’t climb, dismantle equipment, or access concealed duct sections.

When to escalate promptly

Make the issue a priority if grease is near heat sources, electrical equipment, or active food preparation. Escalate promptly if the drip spreads or recurs, or appears with smoke, unusual odour, or reduced extraction. These signs don’t identify a specific fault, but they make a timely assessment more important.

For grease dripping from kitchen exhaust ductwork, avoid DIY sealing or scraping. A surface-level fix can hide the symptom without addressing the source. Arrange a commercial exhaust system assessment to determine whether the issue relates to deposits, a local defect, or duct layout. If the findings point to a layout or system-condition issue, discuss commercial exhaust A&A as a considered next step.

Resolve recurring exhaust-duct grease drips with a system-focused assessment

If a drip returns after the visible area has been cleaned, or the same spot keeps becoming greasy, look beyond the symptom. A commercial assessment should relate where grease appears to the duct route, its connections, the hood configuration, and how the exhaust operates. This wider view helps distinguish a local issue from a concern involving the system layout or condition.

Share observations such as the drip location, when it recurs, which cooking activities are underway, and any recent changes to equipment or the kitchen. These details provide useful context, but they don’t identify the cause by themselves. Consider how the connected components relate to the symptom before deciding whether cleaning, a local repair, or a system change is appropriate.

What a project-focused ductwork assessment can clarify

In a commercial kitchen, duct connections, routing, and hood configuration need to be considered in relation to the premises and its operating requirements. If the findings point to a layout or system-condition issue, commercial kitchen exhaust addition and alteration (A&A) may be a suitable next step. Any tailored ductwork solution should respond to the identified issue and the kitchen’s specific layout. For more context, read this guide to kitchen ventilation A&A.

Air Flow M&E provides commercial exhaust A&A services, commercial kitchen hood installation, exhaust motor installation, and custom-fitted ductwork. These services support project-specific exhaust system changes where the assessed cause calls for them. First identify why grease is escaping, then determine whether these services fit the required work.

Plan the next step for your commercial kitchen

Before arranging the next step, gather the details that make the issue easier to understand:

Where grease appears, and whether the location or amount changes.
When dripping occurs, including the cooking activity and whether the exhaust is operating.
Whether the issue has recurred and what recent cleaning, renovation, equipment, or operational changes may be relevant.

Don’t improvise a repair on concealed or elevated ductwork. If grease dripping from kitchen exhaust ductwork keeps returning, a system-focused approach can help match the response to the cause and avoid treating only the visible effect.

To discuss your commercial kitchen exhaust requirements, get in touch with Air Flow M&E.

Take the right next step for your exhaust system

Grease dripping from kitchen exhaust ductwork is a warning to investigate, not a diagnosis. Deposits, a local duct defect, or a system-layout issue can call for different responses. Protect the affected area, note when and where the drip occurs, and use those observations to guide a professional assessment.

Once the cause is clearer, the next step may be cleaning, attention to a damaged section, or a system modification. Air Flow M&E provides commercial kitchen exhaust addition and alteration services, custom-fitted commercial ductwork, and commercial hood and exhaust motor installation. The right solution depends on the issue identified and the kitchen’s layout.

Start with the cause, then plan a durable response. Discuss your commercial kitchen exhaust requirements with Air Flow M&E and move forward with a clearer plan for your kitchen.

Frequently Asked Questions

Why is grease dripping from my kitchen exhaust duct?

Grease dripping from kitchen exhaust ductwork can result from deposits forming as grease-laden cooking vapour cools, then collecting or escaping through a compromised joint or damaged section. Duct routing and low points may also affect where grease gathers. A drip doesn’t identify one specific fault. Note its location, timing, cooking activity, and whether it recurs to help guide a system assessment.

Is grease dripping from an exhaust duct a fire hazard?

It can signal a fire-safety concern, particularly if grease is accumulating inside the exhaust system or dripping near heat sources. Grease is combustible, so don’t ignore a leak or assume that wiping the visible area resolves the underlying issue. Keep people and food-contact surfaces away from active drips. Arrange prompt assessment, especially if grease is near heat, electrical equipment, or active food preparation.

Can cleaning stop grease from dripping from a kitchen exhaust duct?

Cleaning may help if grease deposits inside the system are contributing to the symptom. It won’t repair a damaged duct, restore a poorly sealed joint, or correct an unsuitable route. If dripping continues or returns after cleaning, the cause may require a closer look at the duct condition and layout. Match the response to the assessed source rather than assuming cleaning alone will solve every leak.

What should I do if grease is leaking from a commercial kitchen duct?

Keep people and food-contact surfaces away from active drips, and treat any slippery floor as a hazard. Record where grease appears, when it occurs, what cooking activity is underway, and whether it has happened before. Take photos from a safe position. Don’t climb, open, or dismantle ductwork. Arrange a commercial exhaust assessment, and escalate promptly if the leak is near heat or electrical equipment.

How do I know whether a duct needs repair or modification?

An assessment can help distinguish a local defect from a wider system issue. Visible damage or seepage at a connection may indicate a local problem, while recurring drips associated with the duct route or kitchen layout may call for modification. These clues aren’t a diagnosis on their own. A commercial exhaust assessment should consider the drip location, duct route, hood configuration, and system operation before recommending a response.

Can I seal or clean a leaking kitchen exhaust duct myself?

Avoid DIY sealing, scraping, or cleaning inside the duct. A surface fix may conceal the symptom without addressing grease buildup, a damaged connection, or a layout issue. Ductwork may also be concealed or elevated, making access unsafe. Keep the affected area clear, document what you can observe safely, and arrange an appropriate assessment. This helps ensure the next step addresses the source rather than just the visible leak.

Does grease dripping mean the exhaust fan is not working properly?

No. A drip alone doesn’t prove that the exhaust fan is faulty. Grease deposits, duct damage, a compromised joint, or the duct route may be involved. Weak extraction or a noticeable change in airflow is useful information to report, but it still doesn’t confirm a fan problem. An assessment should consider the hood, ductwork, and exhaust operation together. Evaluate the fan in context, rather than blaming it based on dripping alone.