What exhaust ductwork do I need for a spray booth in a Toronto home workshop?

A spray booth in a residential home workshop requires dedicated, explosion-proof exhaust ductwork made entirely of grounded metal — no flex duct, no plastic, no fibreglass duct board — and it almost certainly requires a building permit, fire department review, and possibly a variance from Toronto's zoning bylaws.

This is one of the most technically demanding and code-sensitive exhaust projects a GTA homeowner can undertake. Spray finishing produces flammable vapours (from lacquers, solvent-based paints, and conversion varnishes) that can ignite from a single static spark inside a duct. The consequences are catastrophic. Getting this right is not optional.

Duct Material Requirements

All ductwork serving a spray booth must be continuous welded or mechanically fastened galvanized steel or stainless steel, with all joints sealed and every section electrically bonded and grounded to prevent static discharge. The interior must be smooth — no fibreglass liner, no duct board, no flex duct anywhere in the system. Overspray accumulates on duct walls over time, and that residue is fuel. Smooth steel can be cleaned; fibreglass cannot. Minimum 22-gauge steel is typical for residential spray booth exhaust, with heavier gauge (18-20) for longer runs or larger booths.

The duct run should be as short and straight as possible, terminating directly through an exterior wall or roof with a listed exhaust cap that prevents backdraft and spark entry. Every bend increases static pressure and creates a surface where overspray accumulates. Avoid 90-degree elbows where possible — use two 45-degree bends instead. The exterior termination must be located away from any ignition sources, air intakes, windows, and property lines, and must comply with setback requirements under the Ontario Fire Code and Toronto's zoning bylaws.

Fan and Motor Specifications

The exhaust fan must be explosion-proof (spark-proof), with a motor located outside the airstream or rated for use in Class I, Division 1 or Division 2 hazardous locations under the Canadian Electrical Code. A standard furnace blower or bathroom exhaust fan will ignite solvent vapours. The fan must be sized to achieve 100 feet per minute face velocity across the booth opening (or per your booth manufacturer's specifications), which typically means 1,000–3,000 CFM for a small residential booth. The fan motor must be wired by an ESA-Licensed Electrical Contractor using explosion-proof conduit, boxes, and fittings throughout the hazardous zone.

GTA-Specific Considerations

In Toronto, a residential spray booth triggers multiple regulatory layers simultaneously. The Ontario Fire Code (O. Reg. 213/07, Section 5.3) governs spray finishing operations and requires specific booth construction, ventilation rates, fire suppression, and storage limits for flammable liquids. The Ontario Building Code requires a permit for the exhaust system. The ESA requires permits for all electrical work in the hazardous zone. Toronto Fire Services may conduct an inspection. Depending on your zoning classification, operating a spray finishing operation from a residential property may not be permitted at all — this is worth confirming with Toronto City Planning (311 or toronto.ca) before investing in the installation.

Make-up air is not optional here. Exhausting 1,500–3,000 CFM from a workshop will depressurize the space severely, potentially backdrafting any gas appliances (furnace, water heater) in or near the workshop. A tempered make-up air system interlocked with the exhaust fan is required — this must be designed and installed by a TSSA-registered contractor for any gas-fired tempering component.

Practical Cost Range

A properly engineered residential spray booth exhaust system in the GTA — including explosion-proof fan, grounded steel ductwork, make-up air, electrical, and permits — typically runs $4,000–$12,000 depending on booth size, run length, and make-up air complexity. This is not a project to cut costs on.

Hire a professional for every aspect of this project. The ductwork fabrication, fan selection, electrical, make-up air, and permit coordination should all be handled by contractors with documented experience in spray finishing ventilation. Toronto Ductwork can connect you with sheet metal and ventilation contractors through the Toronto Construction Network — browse the directory at torontoconstructionnetwork.com/directory?trade=hvac or get matched for free.