Protecting pets from the silent threat of carbon monoxide

At the Ontario SPCA and Humane Society, we know that pets rely on us to protect their safety, and carbon monoxide (CO) poisoning is an often overlooked risk. Because animals may show signs before pet parents, they can act as early warning signs for your household.  

Protecting your pet from CO not only keeps them safe, but it could also save your life too. 

What is carbon monoxide and why are our pets at risk? 

Carbon monoxide (CO) is a colourless, odourless, tasteless gas produced whenever a fuel-burning appliance or engine (gas, oil, wood, charcoal, propane) is not fully ventilated. 

Because pets are typically smaller, breathe faster, and often spend more time indoors or closer to the floor level of rooms, they may show signs of CO exposure before humans do.  

If CO builds up in your home, garage, or other enclosed space, the results can be sudden and severe for both animals and people. 

The signs to watch for in your pet 

When it comes to pets, symptoms of CO poisoning may be subtle and can easily be mistaken for something else. That’s why vigilance and awareness are key. Typical signs include: 

Behavioural changes 

• Unexpected agitation, anxiety, restlessness, or clinginess.  

• Refusing to enter the house or room where they normally feel comfortable.  

• Lethargy, sleepiness, or seeming “out of sorts” for no clear reason.  

Physical symptoms 

• Vomiting, nausea, or loss of appetite.  

• Uncoordinated movements, stumbling, weakness.  

• Difficulty breathing (rapid, shallow, or laboured breaths).  

• Bright cherry-coloured gums, ears or lips (a less common sign but notable).  

• In extreme cases: seizures, coma, collapse, or permanent damage (hearing, vision, brain).  

If you notice any of these signs, especially in conjunction with a change in environment, such as heating turned on, closed windows, appliance running, treat it as an urgent issue. 

What to do if you suspect exposure 

• Immediately move your pet and yourself to fresh air.  

• Call your veterinarian and describe the symptoms and circumstances. 

• If it’s safe to do so, shut off fuel-burning appliances,and open windows and doors to ventilate. Avoid re-entering the space until cleared. 

• If required, veterinary treatment may include oxygen therapy, monitoring and support for any complications.  

• After the emergency, investigate the source of CO to prevent recurrence. 

Prevention 

Here are steps every household in Ontario should take to reduce the risk of CO poisoning for pets and people: 

• Install properly certified CO alarms on every level of your home, especially near sleeping areas.  

• Test CO alarms frequently and replace them or batteries as recommended.  

• Service fuel-burning appliances annually (furnaces, water heaters, fireplaces, stoves). Ensure proper venting and no blockages from snow, nests, or lint.  

• Never leave a vehicle running in a closed or attached garage, even with the door open, and never let pets stay in there while the engine runs. 

• Never use outdoor fuel-burning devices indoors (barbecues, camp stoves, portable heaters) or in unvented spaces.  

• Be extra vigilant during cold weather when windows are closed and heating systems are in use.  

• Include your pet in your emergency and safety planning.  

If your pet displays sudden behaviour or physical changes, especially during the winter months and when fuel burning appliances are used, don’t wait. Give them fresh air, seek veterinary care, and check your appliances and detectors. Prevention saves lives. 

Let’s keep our fur family safe this season.. 

If this information was helpful, please help us continue to educate about pet health and well-being by making a donation. As a registered charity that does not receive annual government funding, the Ontario SPCA and Humane Society depends on the generosity of donors to change the lives of animals in need.