In 2016, the Ontario Building Code was amended to add a new article for general provisions for laundry-dryer equipment venting in residential occupancies.  Under section 9.32.1.2 (Ventilation of Rooms and Spaces), the following requirements were added as follows:

9.32.1.4.
Venting of Laundry-Drying Equipment
(1) Exhaust ducts or vents connected to laundry-drying equipment shall discharge directly to the outdoors.
(2) Exhaust ducts connected to laundry-drying equipment shall be
(a) independent of other exhaust ducts,
(b) accessible for inspection and cleaning, and
(c) constructed of a smooth corrosion-resistant material.
(3) Where collective venting of multiple installations of laundry-drying equipment is used, the ventilation system shall
(a) be connected to a common exhaust duct that is vented by one central exhaust fan and incorporates one central lint trap,
(b) include an interlock to activate the central exhaust fan when laundry-drying equipment is in use, and
(c) where required by Article 9.32.3.8, be provided with make-up air.
Rationale for Change
Problem/General Background
There are currently no explicit requirements for laundry-dryer exhaust vents.
There are no provisions to require the venting of laundry drying appliances to the outdoors. The discharge of contaminated and moisture-laden air into a building environment can create poor indoor air quality, a fire hazard and excessive humidity. This could cause adverse health effects on the occupants due to the particulates and other contaminants (Volatile Organic Compounds – VOC) and due to possible mould growth. For example, exposure to particulates at certain levels can cause various health effects such as eye irritation and respiratory illnesses as well as trigger asthma and allergy related symptoms. Also, excessive humidity can accelerate a chemical reaction that triggers an increase in the off-gassing from materials and fabrics, and can encourage the growth of viable organisms such as mould and bacteria.
The collective venting of multiple installations of laundry drying appliances, which could be possible in multi-unit residential buildings (common laundry room), may cause a build-up of lint in the exhaust ducts when one or more laundry drying appliances are not in use. Collective venting may also cause short-circuiting of the air to non-operating drying appliances. These situations may cause a fire hazard.
Justification/Explanation
This proposed change harmonizes requirements with the model National Building Code of Canada. The proposed change controls the source of the contaminants by requiring the venting of laundry drying appliances to the outdoors. This would reduce the amount
of particulates and the level of humidity in the indoor building environment, therefore increasing the indoor air quality of the building. Control of the source of the contaminants would also reduce the occurrence of fire and the deterioration of the building assembly.
The change would also allow for proper maintenance of the exhaust vent. Requiring a common exhaust duct with a central exhaust fan creates a continuous negative pressure in the plenum, preventing any back draft or short-circuiting of the air to non-operating drying appliances. This would reduce the risk of fire associated with the build-up of lint.