What the code requires. Dryer vent safety in Port Colborne.

The cause of a dryer fire is almost always the same: a restricted vent that traps heat and ignites accumulated lint. This guide does not rank dryer fires against other causes, because no Ontario or Canadian source it can cite publishes that ranking; it explains the rules that exist to prevent them.

The four things the Code requires of a dryer duct

Ontario's 2024 Building Code Compendium, Division B, Article 9.32.1.3 (Venting of Laundry-Drying Equipment), sets four requirements for a clothes dryer exhaust duct, short enough to quote entire: exhaust ducts or vents connected to laundry-drying equipment shall discharge directly to the outdoors, and shall be independent of other exhaust ducts, accessible for cleaning, and constructed of a smooth corrosion-resistant material. Smooth is a requirement, not a preference: the ribbed foil or plastic accordion hose sold as a dryer connector does not meet the Code's own words for the duct, and rigid metal is what satisfies them. Accessible for cleaning is a design requirement imposed at installation, so a run that cannot be brushed end to end was wrong when it was built. Independent of other exhaust ducts means a dryer must never be teed into a bathroom fan, a range hood or a heat recovery ventilator.

The rule most people expect is not there: the Ontario Building Code prescribes no maximum length for a clothes dryer exhaust duct, no equivalent-length calculation and no deduction per elbow; the widely repeated 35 feet, less 5 feet per 90 degree bend, is the United States International Residential Code and has no force in Ontario. What governs a long or crooked run here is the appliance manufacturer's installation instructions.

Where the duct ends is regulated: Sentence 9.32.3.13.(4) requires exhaust outlets that discharge moist air, clothes dryer exhaust outlets named among them, to sit at least 1 800 mm from air intakes and vented soffits, and where a cap sits below a vented soffit the Code's remedy is not to move the cap but to block the soffit over a measured width from Table 9.32.3.13.-A, from 3 600 mm of soffit for a cap within 300 mm of it down to 1 000 mm for a cap sitting just under 1 800 mm below it.

A clean, unrestricted dryer vent exhausts moisture and heat in one direction: out of the home. A restricted vent recirculates heat back through the lint trap and the drum. Most dryers will overheat and trip a thermal fuse before ignition, but the fuse is a safety device, not a guarantee, and thermal fuses fail.

What the Fire Code asks of you

The Ontario Fire Code (Ontario Regulation 213/07), Division B, Article 2.6.1.3, requires that hoods, ducts and filters subject to accumulations of combustible deposits be checked at intervals not greater than seven days and cleaned if the accumulation creates a fire hazard, and its Sentence (2) expressly lifts that duty for a system that serves only a single suite of residential occupancy. So for a shared laundry, the common laundry room of an apartment or condo building, a laundromat, a retirement home or a hotel, the owner has a legal duty to have the ducts checked at least weekly; for a single-family house or an apartment's own dryer, the Fire Code sets no interval at all.

A homeowner is not outside the Fire Code on this: Article 2.6.1.7 requires heating, ventilating and air-conditioning systems, including appliances, to be operated and maintained so as not to create a hazardous condition, it carries no single-suite exemption, and Division A Article 1.2.1.1 puts the duty on the owner. The accurate sentence for a homeowner is that the Fire Code does not tell you how often to clean your dryer duct, and it does require you to keep the system from becoming a hazard.

A gas dryer adds one more rule: it is a fuel-burning appliance, and the Fire Code's Section 2.16 requires a carbon monoxide alarm adjacent to each sleeping area in a suite where one is installed; a blocked or disconnected exhaust on a gas dryer is a combustion-products problem as well as a lint problem.

Moisture matters mechanically: damp lint clumps and sticks to the duct wall rather than flushing through. The Code addresses the two commonest field defects directly: exhaust ducts shall not discharge into heated or unheated enclosed spaces, so an attic, crawlspace or soffit-cavity termination is prohibited rather than discouraged; all ductwork shall be installed to avoid crushing and permanently supported to prevent sagging, which is the crushed connector behind a pushed-back dryer and the sagging run that pools lint at its low point; and where an exhaust duct passes through or beside unheated space it shall be insulated to prevent condensation in it. How fast lint builds in a given house depends on the run, the load and the appliance; this guide carries no interval it cannot source.

The vent cap and bird-nest risk in spring

A plastic vent flap that has cracked on its hinge or housing, as one can over a winter, does not fully seat. That exposes the duct run to outside moisture and leaves an opening for nesting birds, who add a dense organic obstruction on top of any lint.

Starlings and sparrows nest in open vent caps from late March through May. Open caps (cracked ones, or caps that have lost their flap) are a primary entry point. A starling nest packs into a solid plug and fully blocks exhaust, which is a significant fire risk, particularly on a gas dryer. Removal requires pulling the vent cap, clearing the nest material from the duct run, and confirming the run is clear with an airflow test. A mesh screen installed on the cap afterward lets air exhaust but keeps birds out. A screen that restricts airflow enough to back up lint trades one hazard for another, so the mesh grade matters.

Flex hose versus rigid metal duct

Corrugated foil flex hose, the silver accordion tube that typically connects the dryer to the wall, is not a permanent installation. Its ridges collect lint, it compresses when furniture is pushed against it, and it can creep out of alignment over time. Nothing in the Ontario Building Code recommends rigid metal in so many terms; Article 9.32.1.3 requires that the duct be constructed of a smooth corrosion-resistant material, and smooth rigid metal (galvanized or aluminum) is what satisfies that requirement. A rigid metal run can be fully cleaned with a standard brush; flex hose often has lint permanently embedded in the corrugations that a brush cannot fully clear.

Two credential facts matter for an upgrade job. If the dryer burns gas, disconnecting, moving, reconnecting or servicing it is certificate-gated work under Ontario Regulation 212/01 (Gaseous Fuels): no person may install, alter, repair, service or remove a gas appliance unless they hold a certificate for that purpose, and the business must be a registered contractor: cleaning the duct itself is unregulated, so ask which of the two a quote covers. Dryer vent cleaning is not a compulsory trade in Ontario, but duct installation touches two that are, Residential (low rise) sheet metal installer and Sheet metal worker, whose published scope includes installing ventilation and main ducts in single-family homes; whether replacing one dryer duct in a house amounts to the practice of that trade is not settled by any source, and this guide does not answer it either way.

What dryer vent cleaning costs

Your number depends on duct length, configuration, and what the cap inspection turns up. No verified Niagara or Ontario figure for what this work costs exists in any government, association, or other authoritative source, so this guide publishes none. The way to learn what your job costs is a written, itemized quote from a local contractor, and a second one itemized the same way so the two can be compared line by line. A laundry that sits far from an exterior wall, common in older two-storey layouts, means a longer horizontal run, which takes more time to brush fully and holds more lint per job than a shorter run.