Carbon monoxide has no smell, no colour and no taste, and a pet can show signs of it before anyone else in the house does. An alarm on every level is your best protection. A dog, cat or bird who is unwell indoors and noticeably better outdoors is the warning worth acting on.
Why October matters in Calgary
Calgary gets its first serious cold in October, and that is the week the furnace runs properly for the first time since spring. Six months of dust burns off, a cracked heat exchanger gets its first real workload, a bird’s nest or a wasp nest in a vent stack becomes a blockage, and a flue that worked fine in April does not necessarily work fine now.
The same week, the fireplaces get lit, space heaters come out of storage, cars get warmed up in the morning, and the first wind storm or snowfall of the season raises the chance of a power outage and a generator being started. Every one of those is a potential source, and the furnace itself is only one item on the list.
Bowness has a mixed housing stock, and plenty of the older homes in this part of NW Calgary have detached garages, older appliances and chimneys that have not been looked at in a while. None of that is a reason to be alarmed. It is a reason to get the annual service booked and put a date on the alarm batteries.
Why the pets notice first
Carbon monoxide works by taking the place of oxygen in the blood, so the animals who need the most oxygen for their size are affected soonest.
A dog or cat burns more energy for their size than you do and breathes faster, so they take in more of whatever is in the air relative to their body weight. They are also at home, asleep in the same few rooms, right through a working day when the house is empty. One thing worth clearing up: carbon monoxide mixes evenly through the air rather than settling low, so there is no safe height and no safe corner in an affected room. Birds are more sensitive still, which is why canaries were once carried into coal mines. That does not make a pet bird a substitute for an alarm, but a bird in sudden trouble is an early warning the whole household should act on.
The pattern most worth recognizing is not a dramatic event. It is this: a pet who is repeatedly unwell at home, seems noticeably better when out on a walk or at the kennel, and then goes downhill again a day after coming back. Or two pets in a house becoming lethargic in the same week. Those are not coincidences. They are reasons to have the house checked.
Where it comes from
- A furnace with a cracked heat exchanger, or a blocked or disconnected flue. The classic, and the reason for an annual service by a licensed technician.
- A water heater or boiler venting poorly into a basement or utility room.
- A fireplace or wood stove with a blocked chimney, a closed damper, or a bird’s nest in the stack.
- A gas range or oven used for heating. Never use a cooking appliance to heat a room.
- A vehicle idling in any garage, attached or detached, even with the garage door open. An attached garage is worse, because the exhaust tracks into the house through the shared wall and the connecting door, but a running engine in a closed detached garage is lethal to anyone or anything shut in there with it.
- A generator run in a garage, a shed, a breezeway, or anywhere near a window or vent during an outage. Generators belong outdoors only, at least 20 feet from any window, door or vent, pointed away from the house.
- A barbecue, camp stove or patio heater brought indoors or into a garage. Charcoal in particular produces large amounts.
- Any unvented fuel-burning heater. Kerosene and propane heaters not designed and vented for indoor use.
- Snow blocking an exterior vent. Worth a specific mention in Calgary. After heavy snow or drifting, check that furnace and water heater vents on an outside wall are clear.
What you might notice in a dog or cat
The early signs are frustratingly ordinary, which is exactly the problem:
- Lethargy, sleepiness, or a pet who is slow to get up.
- Reduced appetite.
- Vomiting.
- Weakness, wobbliness or a drunken-looking walk.
- Breathing faster than usual, or seeming short of breath on mild activity.
- Restlessness or unusual whining.
Later or more severe signs:
- Collapse, or an inability to stand.
- Seizures.
- Unresponsiveness.
- Deafness, blindness or disorientation that comes on suddenly.
- Bright red gums. This one is often quoted and is not reliable, so its absence means nothing.
In birds, the first sign is often simply a bird found dead at the bottom of the cage with no warning, or a bird who is suddenly quiet, fluffed up and off their perch. A bird who deteriorates rapidly with no explanation is a reason to get everyone, people included, out of the house and into fresh air.
None of these signs is specific to carbon monoxide. Plenty of ordinary problems look identical, which is why the context matters: is more than one animal affected, did it start when the heating came on, and does the pet improve when they leave the house?
What to do if you suspect it
The order of operations here is different from every other emergency in our blog, because the house itself is the hazard.
- Get everyone out first. People, dogs, cats, birds, everyone, into fresh air outside. Do not stop to pack, and do not shut animals in a room while you investigate.
- On the way out, do not touch anything electrical. No light switches on or off, no appliances, no garage door opener, no doorbell. Do not light a match and do not start a vehicle in or beside the garage. If there is a gas leak as well, any of those can ignite it.
- Call 911 from outside. Do this if your alarm has sounded, if anyone feels unwell, or if any person or animal is collapsed, unresponsive or seizing, and tell them you suspect carbon monoxide. Call your gas utility’s emergency line as well if you can smell gas. Make every call well away from the building.
- If no alarm has sounded but you suspect it anyway, still get out, and still call. Ask the fire service or your gas utility to check the house, and have the heating system inspected by a licensed technician before anyone sleeps there again.
- Do not go back in until the fire service or the utility says the house is clear. That includes going back for a pet carrier. Carry a cat inside a zipped coat or a bag, keep dogs on a leash, and borrow a box from a neighbour rather than re-entering.
- Then phone us and bring the animals in. Any pet who has been in a house with a confirmed or suspected carbon monoxide problem needs assessing, even one who looks fine in the open air.
- Tell us the timeline. When the heating came on, when the pet became unwell, how long they were in the house, and whether anyone else in the household has had headaches, nausea or unusual tiredness.
Fresh air is the first and most important thing anyone does for a carbon monoxide patient, and you will have already started it by getting them outside. Come in through our urgent and emergency care, where oxygen, fluids and monitoring are the core of what these patients need, and our pet diagnostics team can assess the blood, the heart rhythm and the chest. Some animals need watching for a day or two, because effects on the brain and heart can appear after the obvious signs have settled, and that follow-up is where our medical services team comes in.
Monday to Friday we are here 9:00 AM to 7:00 PM, Saturday 9:00 AM to 5:00 PM, and Sundays and statutory holidays we are closed. Carbon monoxide clusters on cold nights, storm nights and outages, which is to say the hours this clinic is dark. If that is when it happens, whether overnight, early morning, evening, Sunday or a holiday, head for an emergency hospital that is open and call ahead as you go. If anyone in the household is affected as well, the fire service comes first.
Preventing it, which is almost all of the job
- Install CSA-approved carbon monoxide alarms on every level, including outside the sleeping areas and near the basement. One in the hallway is not enough in a two-storey Bowness house with a finished basement.
- Press the test button on every alarm once a month, and change the batteries at least once a year, when you set the clocks back. Do not wait for a chirp to remind you.
- Check the replace-by date on the alarm itself. The sensors expire, usually after seven to ten years, and an expired alarm can look and sound perfectly healthy.
- Book the annual furnace service with a licensed technician before the cold sets in, and have the chimney and any wood stove inspected and swept.
- Never idle a vehicle in any garage, attached or detached. Back it out into the open air first, even on the coldest morning, and never leave a pet in a running vehicle or shut in a garage.
- Keep generators far from the house and never in a garage, shed or carport, even with the door open.
- Never bring a barbecue or camp stove indoors or into a garage, however cold it is.
- Do not heat a room with the gas oven.
- Clear snow and ice from exterior vents after every heavy snowfall.
- Keep pets out of the furnace room, which is also good practice for the loose insulation, cords and chemicals usually stored in there.
While the house is on your mind, the first cold snap changes several other things for a dog or cat. Our guide on what changes for your pet in the first cold snap covers the outdoor half of the same few weeks.
Frequently asked questions
Will a carbon monoxide alarm protect my pets?
Largely, yes, and it is the single most effective thing you can do. The one caveat is that alarms are set to protect people, and small animals and birds may be affected at lower concentrations, or sooner, than the alarm threshold. So an alarm plus attention to a pet who is unwell indoors and better outdoors goes a good deal further than an alarm on its own.
My dog is lethargic and off his food. How would I know if it is carbon monoxide?
You would not, from the signs alone, and plenty of common problems look the same. The clues are contextual: more than one animal affected, the timing lining up with the heating coming on, people in the house with headaches or nausea, and the pet improving when they are out of the house. Phone us and mention all of it, because it changes what we look for.
Is it dangerous to warm the car up in the garage with the door open?
Yes, in any garage. An open door does not clear exhaust anywhere near quickly enough. In an attached garage the gas also moves into the house through the shared wall and the connecting door, and in a closed detached garage it simply fills the space the engine is running in. Back the vehicle out before you start it, and never leave a pet in a running vehicle or shut in a garage.
My bird died suddenly and nothing seemed wrong. Should I be worried about the house?
It is worth taking seriously. Birds are far more sensitive to carbon monoxide and to other fumes than we are, and a sudden unexplained death in a bird is one of the recognized warnings. Get fresh air into the house, check your alarms, and have the heating system inspected.
Do pets recover fully?
Many do, particularly when they are out of the house quickly and assessed the same day. Effects on the brain and the heart can appear or persist after the initial signs settle, which is why we often want to recheck a patient over the following days rather than sending them straight home and hoping.
Are candles, fireplaces and space heaters all the same risk?
No. Candles are a burn and a fire risk rather than a meaningful source of carbon monoxide. A fireplace or wood stove with a blocked or closed flue is a genuine source. Electric space heaters do not produce carbon monoxide at all, though they are a burn and fire hazard around pets; unvented fuel-burning heaters are the ones to avoid indoors.
What should I ask the technician at the annual service?
Ask them to check the heat exchanger, the venting and the flue specifically, and to confirm your carbon monoxide alarms are positioned correctly for your layout. If your home has an attached garage, ask about the seal on the connecting door. A wellness program visit is also a sensible time to mention anything that has changed about your pet since the heating came on.
Speak to the team at Bowness Animal Hospital
If your carbon monoxide alarm has sounded, or your dog, cat or bird has been unwell in a way that improves when they leave the house, get everyone out into fresh air, call 911 or your gas utility from outside, and then phone us. Outside our hours, go to the nearest open emergency hospital and call them on the way.
Published by the team at Bowness Animal Hospital.
This article is for general educational purposes only and is not a substitute for an in-person veterinary examination or advice about your individual pet. If you have an urgent concern about your pet, contact Bowness Animal Hospital or your nearest emergency veterinary hospital right away.
Bowness Animal Hospital
Unit #52, 7930 Bowness Rd NW, Calgary, AB T3B 5C2
Phone: (587) 391-3911
Email: bownessvet@shaw.ca
Hours: Monday to Friday 9:00 AM to 7:00 PM; Saturday 9:00 AM to 5:00 PM; Sunday and statutory holidays closed