Preventing Harmful Fumes with Exhaust Depressurization Testing

Published on December 05, 2018

As homes continue to be built to even higher levels of air tightness, it has become more important than ever to make sure that harmful fumes aren’t spilling into your home. This is especially important in homes with a wood stove, as combustion spillage can cause serious air quality and health concerns.

By having a Registered Energy Advisor conduct an Exhaust Depressurization Test, the exact pressure levels of the home are tested, ensuring that home has enough positive pressure on the interior so that smoke will leave through the chimney.

Balancing Interior Pressure with Ventilation

Homes that have exhaust devices such as: bath fans, dryers, central vacs, and even range hoods in the kitchen, are susceptible to lower levels of interior pressure. This is due to the potential of exhaust devices being able to push too much air out of a home - depressurizing the interior -  and if the home is sufficiently airtight, then not enough new air will be able to replace the exhausted air in enough time for the home to re-pressurize. 

Having a low level of interior pressure can be very detrimental to a home equipped with a wood stove, as wood stoves rely on the interior air to feed the fire and help push the products of combustion up and out of the chimney.

When an Exhaust Depressurization Test is Required

For all new homes built with a wood stove, an Exhaust Depressurization Test is required in order for the home to meet Ontario Building Code. An Exhaust Depressurization Test is also recommended for homes equipped with a naturally aspirated appliance, such as some gas fired water heaters.This is important as it not only indicates if hazardous fumes are able to intrude into the home’s interior, but it also ensures that no backdraft combustion will be able to occur from the wood stove - posing a potential and serious risk of fire.

It is helpful to think of a home as a part of a system, where each modification or change to one part has an effect on the rest of the system as a whole. When new sources of ventilation or new exhaust devices are installed in an already built home, an Exhaust Depressurization Test can verify that the new additions don’t lower interior pressure levels to the point where air quality suffers or combustion spillage can occur.

Due to their extensive experience and training, a Registered Energy Advisor can help homeowners determine their best options for improving air quality - through high levels of air sealing and sufficient ventilation. They are also able to ensure that the level of air tightness in the home is ample enough to maintain a high level of energy efficiency, as well as locate which areas of the home are leaking air.

How Combustion Spillage is Monitored

When an Exhaust Depressurization test is required, and the home is equipped with a wood stove, a Registered Energy Advisor starts by monitoring the resting pressure levels of the home. After a normal reading has been acquired, the advisor turns on all sources of ventilation and exhaust, while continuing to monitor interior pressure levels. If the level of pressure lowers by a significant 5 Pa during this test, then the advisor becomes aware of the dangerous combustion spillage happening in the home.

From this point, an advisor can further determine what is causing the depressurization, and what solutions could be taken to prevent it from happening further. Each home is different and has different factors affecting it, and as a result there is no cookie-cutter way of maintaining positive interior pressure that can be applied to every home. Some homes may need a higher level of air sealing, whereas some homes may need adjustments to their ventilation locations or amounts.

By being able to evaluate the entirety of a home and understand how each modification or retrofit works to affect the system as a whole, Registered Energy Advisors are able to provide homeowners with a comprehensive outlook of their home’s level of energy efficiency, as well as what options for improvement would be the most cost-effective.