Kitchen Exhaust Ductwork and Make-Up Air in Markham
Make-up air is the replacement air a building feeds back into a kitchen to balance what the exhaust fan removes. Markham Hood Cleaning cleans the kitchen exhaust ductwork and reads the make-up air side feeding it, because a hood starved of replacement air cannot capture however clean it is. This scope is the kitchen grease path and its supply air. Building-wide HVAC and residential air duct cleaning are a different trade and are not offered here.
Air has to come from somewhere
An exhaust fan cannot create air. Every cubic metre it pulls out of the hood has to be replaced by a cubic metre coming in from somewhere, and the building either supplies it deliberately through a make-up air unit or it finds it accidentally through gaps: the back door, the dining room, the service corridor, the ceiling void.
When supply falls short, the kitchen goes negative. The fan is now working against a partial vacuum, so it moves less air than its rating, and less air at the hood means less capture. The plume that should be pulled into the canopy instead rolls out at the lip. Grease that should be going up the duct lands on the ceiling, the walls, the light fittings and the staff.
The symptoms are recognisable and they are usually blamed on the wrong thing. Doors that pull hard or whistle. Pilot lights blowing out. Smoke visible along the front of the hood. Air conditioning that cannot hold temperature because it is cooling replacement air dragged in from outside. Every one of those points at pressure, not at dirt, and no amount of degreasing will change any of them.
A grease problem vs an airflow problem
They produce similar complaints and need completely different work. This is how they are told apart.
| What you observe | Points to grease | Points to airflow |
|---|---|---|
| Capture got worse gradually | Yes. Filters and plenum load steadily over weeks. | Less likely, unless a supply fan is failing slowly. |
| Capture got worse overnight | Rarely. | Yes. A supply unit switched off or a belt gone. |
| Back door is hard to open | No relationship. | Strong signal. The kitchen is running negative. |
| Duct reloads much faster than it used to | Possibly a menu change adding grease. | Possibly slow airflow letting droplets settle in the run. |
| Only one hood in a bank misbehaves | Likely. Filters missing or a blocked branch. | Possible if a damper has closed on that branch. |
| Fan is noisy or vibrating | Yes. A coated blower wheel loses balance. | Yes. A fan starved of air runs rough as well. |
Where the answer is airflow rather than grease, the report says so and names what needs looking at. Selling a cleaning for a pressure problem fixes nothing.
Where make-up air goes wrong in Markham buildings
Three patterns account for most of it, and two are nothing to do with the kitchen equipment.
The unit is switched off. Make-up air units cost money to run because they heat outdoor air in winter, and they get turned down or off to save on gas. The kitchen goes negative the same day and stays that way until somebody connects the two facts. This is the single most common finding, and the fix costs nothing.
The kitchen grew and the supply did not. A plaza or mall unit fitted out for one hood gets a second one added as the menu expands, or a bigger fan goes on the roof to fix a capture complaint. Exhaust capacity goes up, supply capacity stays where it was, and the imbalance gets worse rather than better. Adding fan capacity without adding supply is the classic way to make a capture problem harder to solve.
The supply intake is blocked or filthy. Intake screens sit outside collecting leaves, snow and, on a roof next to a kitchen fan, the discharge from that same kitchen. Supply filters get changed far less often than anybody plans. Both restrict what the unit can deliver even when it is running exactly as intended.
Where the finding is mechanical, it is reported for the building's HVAC contractor to act on. Markham Hood Cleaning does not commission make-up air units or balance building systems, and says so rather than working outside its trade. What it does do is clean the kitchen exhaust ductwork, described in full on the kitchen exhaust cleaning page, and tell you honestly when cleaning is not the answer.
How much does this cost in Markham in 2026?
Markham Hood Cleaning quotes exhaust ductwork with the rest of the system after a free walk-through, starting at $385 per visit for a single-hood kitchen up to ten feet, and the make-up air assessment is part of that walk-through at no extra charge.
The assessment is free because it protects both sides. A kitchen that pays for a cleaning expecting its capture problem to disappear, when the actual cause is a make-up air unit switched off in a plant room, ends up unhappy with work that was done correctly. Establishing which problem is which before quoting avoids that entirely.
Where the answer is genuinely grease, the ductwork is quoted as part of the full path. Where it is airflow, the report goes to the kitchen and to the building, and no cleaning is sold to fix it.
Next step: call 289-806-9117 or request a written quote. Mention whether the back door has become hard to open. It is a better diagnostic than most instruments.
Exhaust ductwork and make-up air in Markham: frequently asked questions
Do you clean building HVAC or office air ducts?
No. Markham Hood Cleaning works on the kitchen grease path and the supply air feeding it. Office air handling, residential ductwork and building-wide ventilation are a separate trade with separate equipment, and this business does not offer them. Anywhere this site says ductwork, it means kitchen exhaust ductwork.
How can I tell if my kitchen is running negative?
Open the back door part way and let go. If it pulls itself shut hard, or if opening it changes how the hood behaves, the kitchen is drawing air through it. Whistling at door edges and pilot lights that will not stay lit point the same way. Any of those is worth mentioning when booking, because it changes what the walk-through looks at first.
Will a bigger exhaust fan fix a capture problem?
Usually not, and it often makes things worse. A larger fan pulling from a kitchen that already cannot get enough replacement air simply increases the deficit, so the extra capacity never materialises and the room goes further negative. Supply has to be sorted first. That answer costs nothing and saves the price of a fan.
Does make-up air affect how fast the duct gets dirty?
It can. Airflow that is too slow lets droplets settle in the horizontal run rather than carrying them to the fan, so a starved system loads its duct faster than a healthy one on the same menu. A duct that needs cleaning noticeably sooner than it used to, with no menu change to explain it, is worth checking on the supply side.
Who fixes it if the make-up air unit is the problem?
The building's mechanical or HVAC contractor. Markham Hood Cleaning documents the finding, describes what was observed, and hands it over. Many issues turn out to be a unit switched off or a control setting, which the building can resolve without a contractor at all once somebody points at it.