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Commercial · Machine Shops & Light ManufacturingMachine Shop & Light Manufacturing HVAC
Machine shop and light manufacturing HVAC comes down to one rule: every cubic foot of air your fume arms, mist collectors and wall fans push outside has to be replaced with heated outdoor air, and Ontario Regulation 851 says so in plain words. Get that balance right and the rest follows, because the unit heaters stop backdrafting, the doors stop whistling and the office stops smelling like coolant. We heat, cool and ventilate shops across Burlington, Oakville, Milton, Hamilton, Mississauga and Brampton, and we size replacement air to the exhaust we measure on site, not the exhaust on an old drawing.
Start with the exhaust, because it sets everything else. Section 128 of Regulation 851, the Industrial Establishments regulation under the Occupational Health and Safety Act, requires replacement air for air that is exhausted, heated when necessary to hold the minimum workplace temperature, which section 129 sets at 18°C for most enclosed workplaces. A welding fume arm or a mist collector ducted outdoors counts; a mist collector that filters the air and returns it to the shop removes nothing from the building and needs none. Add up the fans that discharge outside, and that total is the size of your make-up air unit.
Heat is the second half of the load, and in a machine shop most of it comes from the machines. Every kilowatt a spindle motor, hydraulic pack or heat-treat oven draws ends up as heat in the room, and a rotary screw compressor turns nearly all of its electrical input into warm air. That is why a shop can need cooling in April and still need the unit heaters at six on a January morning before the machines warm up. The cheapest fix is often sheet metal: duct the compressor's cooling air outdoors in summer and back into the shop in winter through a damper.
Split the building into two systems and keep their air apart. The front office belongs on its own rooftop unit or split system with its own return, and the shop floor on gas unit heaters plus ventilation, with spot cooling aimed at operators instead of trying to air-condition a room full of open bay doors. An inspection room is the exception: parts are measured against a reference temperature of 20°C, so a CMM room gets its own small system that holds that number all year. Where oil mist, coolant spray or grinding dust hangs in the air, we specify separated-combustion heaters that pipe their combustion air in from outside.
Oil mist is what shortens equipment life in these buildings. It films the filters and the cooling coil, dust sticks to the film, and airflow drops until the coil ices or the heat exchanger overheats and trips its limit. Shop filters get checked monthly and changed when loaded, which is a different schedule from the quarterly one that suits an office, and coils get degreased, not just rinsed. Our warehouse and industrial HVAC page covers the large-volume heating side, and the commercial HVAC hub lists everything else we service.
Equipment we install and service
A rooftop or wall-mounted cabinet that brings in outdoor air, heats it with a gas burner and delivers it to the shop floor to replace what the fume and mist exhaust removes. It is interlocked so it runs whenever the exhaust runs. We size it from measured exhaust airflow and set the discharge so it does not blow across a welding hood or stir up settled dust, both of which Regulation 851 names.
Suspended gas heaters that draw combustion air through a sealed pipe from outdoors instead of from the shop. That keeps oil mist, dust and solvent vapour out of the burner; chlorinated solvents and some cutting-fluid additives turn acidic in a flame and eat a standard heat exchanger from the inside. Each one is a TSSA-regulated gas appliance installed to CSA B149.1.
Packaged heating and cooling for the front office, lunchroom and inspection room, kept on its own return so it never recirculates shop air. Check the nameplate voltage before anyone orders a replacement: Ontario industrial units are commonly fed at 600 V three-phase, and a 208 V unit will not connect to that service without a transformer.
Ducted spot cooling or a small split aimed at a fixed workstation, a CMM room or an electrical cabinet, plus the wall and roof fans that purge heat in summer. Wall fans are cheap cooling when it is 20°C outside and a liability in January if nothing replaces the air they remove.
What goes wrong in these buildings
- The man door slams and the bay door is hard to lift whenever the weld-fume fans are on.
- Our unit heaters go out on a limit and the tech says the heat exchangers are caked with oil.
- The office smells like coolant by ten in the morning and the front staff get headaches.
- It is 30°C at the machines in July and the compressor room is worse.
- A Ministry of Labour inspector asked how we replace the air our collectors exhaust and I did not have an answer.
- The rooftop unit over the office tripped out again and the filters were black after six weeks.
How it works
We list every fan and collector that discharges outdoors, measure what each one moves, and read building pressure with the doors shut and everything running. You get the numbers on one sheet with the nameplate data for each heater and rooftop unit. That sheet is the basis for the quote and a useful record if an inspector asks about replacement air.
Replacement air, heater changes, spot cooling and the filter schedule are priced as separate lines so you can do them in order of urgency. Cost is driven by the airflow you need to replace, gas and electrical capacity at the building, and roof or wall access; there is no honest flat rate, so the number comes after the site visit. General price guidance for smaller repairs is on our pricing page.
Gas piping, curb work and crane lifts are booked for a shutdown, a weekend or the gap between shifts. New gas appliances and new roof openings are permit work through the municipal building department, electrical connections fall under ESA, and we handle that paperwork. To start, contact the shop with your exhaust fan list or a few photos of the roof.
Common questions
Does a mist collector need make-up air?
Only if it discharges outdoors. Most machine-mounted mist collectors filter the air and return it to the shop, so they take nothing out of the building. A central system ducted through the roof or wall does, and so does welding fume extraction, a parts-washer exhaust and any wall fan. Add those airflows together and you have the replacement air the shop needs when everything runs at once.
Can we air-condition the whole shop floor?
You can, but it rarely pays in a building with dock doors, high ceilings and machines rejecting heat all day. The decision rule we use: condition people and precision, ventilate everything else. That means spot cooling at fixed workstations, a held temperature in the inspection room, and exhaust plus tempered replacement air for the open floor. Full-floor cooling makes sense when tolerances or materials demand a stable room temperature.
How often should filters be changed in a machine shop?
Check monthly and change when the filter is visibly loaded or the pressure drop across it has doubled. Oil mist blinds a pleated filter far faster than office dust, so a quarterly contract schedule leaves the unit starved for air two months out of three. We usually fit MERV 8 pleated filters in shop-side units, because a finer filter loads faster without protecting the coil any better from oil.
Do you install dust, mist or weld-fume collection systems?
No. Capture hoods, collectors and their ductwork are designed by industrial ventilation specialists, and combustible dust has its own rules. Our scope is the building side: the make-up air unit that replaces what those systems exhaust, the heaters, the office and inspection-room cooling, the gas piping and the controls that interlock them. We work from the collector supplier's airflow figures and verify them on site.
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