Outage Improvisations That Endanger Pets: Unvented Heaters, Candles, and Dry Ice

Skip the indoor fuel-burning heater and the candles. ASHRAE, CDC, Ready.gov and CPSC each advise against some form of indoor combustion heating, and NFPA, USFA and the American Red Cross say to use flashlights, not candles. Dry ice is different: the Compressed Gas Association (CGA) sets ventilation conditions for it rather than banning it. Add battery-backed carbon monoxide (CO) alarms on every floor. Carbon monoxide and the carbon dioxide from dry ice are two different hazards, and the difference decides where an alarm goes.

Everything here happens indoors, in the room the animals are in. If the problem is a generator running outside, see what a machine running outdoors can still do to the air inside.

If a CO alarm sounds, people go outside first

Human life comes first. Every source below is written for people, and where any instruction would have you take a personal risk to reduce an animal’s risk, follow the instruction for people.

CPSC’s consumer sheet on generators and carbon monoxide (CPSC468 0322) says: “DON’T ignore a CO alarm when it sounds. Get outside immediately, then call 911.” It lists the symptoms of CO poisoning as headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion.

NFPA adds three steps: move to fresh air outdoors or by an open window or door, make sure everyone inside is accounted for, and call for help from the fresh air location. UL Solutions, writing for code officials, says: “Do not reenter the premises until the emergency services responders have given their permission.”

None of those instructions has a pet exception. In our view, if an animal is in a back bedroom and you already have symptoms, going deeper into the building can turn one casualty into two, and responding crews, who carry breathing apparatus, are better placed to go in. You may end up on the sidewalk while your animal is still inside. The way to make that less likely is preparation: alarms that work, and animals’ locations, crates and leashes sorted in advance. Our drill for getting animals out of a building fast covers that.

Carbon monoxide does not pool at pet height; carbon dioxide does

A common assumption is that animals are low, bad gases are low, so animals breathe the worst air. That is half wrong.

Carbon monoxide. The ASPCA, writing about pets and carbon monoxide, says: “Carbon monoxide is roughly the same density as room air, so animals close to the ground are at no more risk than taller animals.” The exception it names is birds, which it says are more sensitive to carbon monoxide because of their respiratory system. The bird risk is respiratory, not gravitational.

Carbon dioxide. The Compressed Gas Association (CGA) describes carbon dioxide gas as colorless, odorless and about 1.5 times as heavy as air. Its dry ice storage guidance says: “Ventilation systems should exhaust from lowest level and make up from higher point.” That instruction only makes sense for a gas that collects low.

The difference decides where a detector goes. If you believed the merged version, you might mount a CO alarm near the floor where the dog sleeps, which would be a detection failure dressed up as pet care. NFPA’s instruction is to follow the manufacturer’s instructions for placement and mounting height. Keep the two gases separate below: the heater section is about carbon monoxide, and the dry ice section is about carbon dioxide.

Improvisation one: burning fuel indoors for heat

This improvisation carries the carbon monoxide risk. It comes in several shapes: a kerosene heater, an unvented propane radiant heater, a camp stove or lantern brought inside, a charcoal grill, and a gas oven with the door open.

What the agencies say about each shape

• Gas oven or stovetop. Ready.gov says not to use a gas stove or oven to heat your home: it raises the risk of carbon monoxide poisoning, and can also cause fires and burns and damage the appliance. CDC says never to heat your house with a gas oven, and not to cook or burn anything on a stove or fireplace that is not vented. USFA says never to use an oven to heat your home. The American Red Cross also says not to use a gas stove to heat your home, and not to use outdoor stoves indoors for heating or cooking.
• Charcoal. CDC says never to burn charcoal indoors, and that charcoal of any color (red, gray, black or white) gives off CO. A grill that has stopped flaming has not stopped emitting.
• Camp stoves and portable heaters. CDC says never to use a portable gas camp stove indoors and not to use portable flameless chemical heaters indoors. No visible flame does not mean no carbon monoxide. CPSC’s carbon monoxide page says not to use portable heaters or lanterns while sleeping in enclosed areas such as tents, campers and other vehicles, and adds that this is especially important at high altitudes, where the risk of carbon monoxide poisoning is increased. If your plan involves sleeping in a vehicle with an animal, that applies.
• Portable generators. CPSC468 0322 says not to operate a portable generator inside a home, garage, basement, crawlspace, shed or on a porch, and never to leave a car running in an attached garage. The placement and exhaust rules for generators are on the generator page. Do not carry any number from that page onto this one.

ASHRAE: unvented heaters as a class

The most current statement comes from ASHRAE, the professional body for heating, ventilating and air conditioning engineers. Its Position Document on Unvented Combustion Devices and Indoor Air Quality was approved by the ASHRAE Board of Directors on June 4, 2026. It says:

• Vented combustion devices result in less exposure to combustion-related pollutants than unvented ones.
• “Unvented combustion devices should never be used as the primary/sole source of heating.”
• Consumers who want to reduce the risk of adverse health effects from combustion products should not use unvented devices.
• CO alarms should be installed in all homes with unvented combustion devices.
• Unvented room heaters should not be fueled with liquid fuels such as kerosene, alcohol, gasoline or diesel.
• Where an unvented device is used, it should follow the manufacturers’ instructions and local codes, with installation by a qualified installer.

It also recommends that existing unvented heating devices that do not meet those positions be removed from operation.

Two scope notes keep these from traveling as a different claim. The document excludes candles, incense and solid-fuel devices, so none of it is about a candle, wood stove or fireplace. And it is written for people and indoor air quality generally; it does not address animals.

CPSC’s rules for people who already own a kerosene heater

CPSC has not written the unvented heater out of existence. Its publication CPSC Stresses Kerosene Heater Safety (Pub. 5052, revised April 2011) is written for someone who will use one. It says kerosene heaters produce low levels of pollutants such as carbon monoxide and nitrogen dioxide, and that exposure may be harmful, especially to people with chronic respiratory or circulatory problems.

Its rules include using only water-clear 1-K grade kerosene and never gasoline, operating the heater in a room with the door open to the rest of the house, following the manufacturer’s instructions, and never refueling the heater inside the home. If you must operate it with the door closed, or the home is relatively new and tight, or older but winterized to cut air leakage, it says to open an outside window about one inch so fresh air dilutes the pollutants.

Note what that document is doing. Its heading is about reducing exposure, it says exposure may be harmful, and it never says the result is safe or mentions an animal. A cracked window is a dilution measure published for humans. It is not a permission slip for a room with a parrot, a rabbit or a sleeping dog in it.

CPSC’s 2011 document and ASHRAE’s 2026 one do not conflict. One is instructions for a person who owns the appliance. The other is a position on whether to use it.

“Indoor safe” on the box, and what the safety shutoff actually senses

Propane heaters are marketed as indoor safe. Mr. Heater’s Portable Buddy product page calls it an “Indoor safe radiant propane heater” with an oxygen depletion sensor and tip-over shutoff. That is a claim about a product category and its features. It is not a statement about animals.

Look at what the sensor is named for. Section G2445, as adopted in the Texas Windstorm Insurance Association Residential Code 2024 and published by UpCodes, requires unvented room heaters to have an oxygen-depletion-sensitive safety shutoff that stops the gas when oxygen falls to a manufacturer-specified level, but not lower than 18 percent. The trigger is an oxygen concentration. ASHRAE recommends such sensors and, in the same list, recommends that consumers who want to reduce exposure not use unvented devices at all. Both positions stand.

The same code section goes further than a recommendation: unvented room heaters may not be the sole source of comfort heating in a dwelling unit. Whether your jurisdiction has adopted that provision is a question for your local building or fire department.

None of this tells you the appliance is fine in a closed room with a cat in it.

Clearances and permitted locations belong to the manual and the local code

Clearance to combustibles, minimum room volume, permitted rooms and input rating are set by the appliance manual and by the fire and fuel gas codes your jurisdiction has adopted. ASHRAE itself points to manufacturers’ instructions, local codes and a qualified installer.

The generic figures the fire agencies publish answer a different question, the fire question. USFA says to keep anything that can burn at least 3 feet from heat sources including fireplaces, wood stoves, radiators, space heaters and candles. NFPA’s Heating Safety tip sheet (©NFPA 2017) gives the same distance, three feet or one metre. Those are clearances for things that burn, not carbon monoxide clearances, and they were not written with a pet bed, bird cage stand or plastic crate in mind. For anything about your model, call the manufacturer; for what your jurisdiction permits, call your local building or fire department.

One statistic that changes how you rank the risk

USFA reports that home portable heater fires were only 3% of all home heating fires annually for 2017 to 2019, but accounted for 41% of fatal home heating fires. That is a statistic about people, not pets. The heater you drag out of the garage for one cold night is over-represented in the worst outcomes. For the non-combustion side of staying warm, see our cold-weather preparation page, and for power stations that run electric loads without a flame, the equipment answer.

CO alarms apply to every improvisation above

If anything in your house burns fuel, alarms are not optional, and the requirement is not pet-specific.

• Battery backup. CPSC468 0322 says: “DO install battery-operated CO alarms or CO alarms with battery backup outside sleeping areas, and on each floor of your home. Test alarms monthly.” In our view, an alarm with no battery backup may not work when the power is out.
• Siting. NFPA says CO alarms belong in a central location outside each sleeping area and on every level of the home, and in other places required by codes or standards. It recommends interconnecting them so that when one sounds, all sound. Then comes the sentence that settles the pet question: “Follow the manufacturer’s instructions for placement and mounting height.”
• Labels and testing. NFPA says to choose an alarm carrying the label of a recognized testing laboratory, to test monthly, and to replace alarms according to the manufacturer’s instructions. It also suggests calling your local fire department’s non-emergency number to learn what number to call if a CO alarm sounds. Do that this week, not during an outage.
• Which code. Household CO alarm requirements are in NFPA 72, National Fire Alarm and Signaling Code, whose current edition is 2025 according to NFPA’s product page. UL Solutions says NFPA 72 incorporates the CO alarm requirements previously covered in NFPA 720.

CO alarms are investigated to UL 2034. UL Solutions says the UL 2034 sensitivity test is based on a 10% COHb level (a human blood measurement) that may be imperceptible or produce only a slight headache, and to keep that in mind when an alarm activation is reported. No source cited here describes a consumer alarm as calibrated for animals. That is not a reason to skip the alarm. It is a reason to treat any activation as a whole-household event, and not to reason from “the pet seems fine” to “the air is fine.”

Three things not to do with an alarm because of a pet: do not mount it low; do not skip a level of the house because only the pets are on it; and do not treat a bird as an early-warning device. A bird’s greater sensitivity is a reason to protect it, not to give it a job.

Improvisation two: candles

Candles are a light improvisation, not a heat one, and the agencies’ answer is shorter than for heaters. They do not ask you to be careful with candles in an outage. They ask you not to use them.

• NFPA’s Candle Safety tip sheet (NFPA 2025): “Have flashlights and battery-powered lighting ready to use during a power outage. Never use candles.”
• USFA’s severe weather page: “Never use candles for emergency lighting. Use flashlights and stock up on extra batteries.” Its candle page also says to use flashlights, not candles, in a power outage.
• The American Red Cross power outage guidance says to use flashlights, not candles.

Three bodies, one instruction, no conditions.

How big the problem is

For 2020 to 2024, NFPA’s candle page reports these figures:

• An annual estimated average of 5,894 home structure fires whose heat source was candles, causing an annual average of 63 civilian deaths and 532 civilian injuries.
• Candles were the heat source for 2% of reported home fires, 2% of home fire deaths and 5% of home fire injuries.
• Over half of candle fires started when something flammable (furniture, mattresses, bedding, curtains, decorations, paper or clothing) was too close to the flame.
• In 21% of home structure candle fires, the candle was left unattended, discarded or otherwise misused.
• Over a third of candle fires (36%) started in the bedroom. Sleep was a factor in 11% of candle fires, but in 34% of candle fire deaths and 17% of candle fire injuries.

Two of those failure modes are ones a pet can create: something flammable moved too close, and a flame left unattended. In our view, the sleep figures matter most in a long outage, when the household and the animals may share one warm room.

The placement problem is the part pet owners have to solve

USFA says: “If you do use lit candles, make sure they are in stable holders and place them where they cannot be knocked down easily.” NFPA’s tip sheet says to use sturdy holders that will not tip over easily, and to keep candles at least 1 foot (30 centimeters) away from anything that can burn.

Read “where they cannot be knocked down easily” as a cat owner. The places people pick as out of reach, such as counters, mantels, bookshelf tops and toilet tanks, are surfaces a cat treats as a route. A dog’s version is different but just as real: a wagging tail at coffee-table height, a startled scramble when a transformer bangs outside, a nose that investigates anything new at floor level. This is our own reasoning, not a published statistic. The usable test is a question: is there any surface in this room the animal cannot get onto, and is that where the flame is? For most cat households the answer is no, which is the argument for the swap rather than for a better shelf.

Clearance numbers differ; use the larger one

NFPA’s tip sheet and USFA’s candle page both say 1 foot (12 inches) from anything that can burn. But USFA’s heating page groups candles with other heat sources under a 3-foot rule. The same agency publishes both figures. The larger one satisfies both. If the candle is anywhere near a pet bed, blanket, cardboard scratcher or pile of paper, use it.

Two more candle rules for an outage house

• NFPA: “Never use a candle if oxygen is used in the home.” If anyone in the household is on home oxygen, that is a hard stop.
• NFPA also says to blow out all candles when you leave the room or go to bed, and to avoid candles in the bedroom and other areas where people may fall asleep.

Birds: the second candle hazard is not fire

A candle in a room with a bird is two hazards, and the second does not need to tip over.

The Merck Veterinary Manual chapter on toxicoses of pet birds (Sharman M. Hoppes, DVM, DABVP (Avian); reviewed September 2021, updated May 2026) lists votive candles among aerosols and fumes that may be irritating or toxic to caged birds.

The Association of Avian Veterinarians (AAV) client handout Protecting Your Pet Birds from Household Dangers (2022) explains why: the avian respiratory tract is extremely sensitive to inhaled chemicals, and products that cause no problem for people or other mammals can be highly toxic to birds, with effects that range from mild illness to sudden death. Its list of unsafe airborne products includes scented candles, air fresheners, aerosols, paints, gasoline fumes, mothballs and cleaning products such as ammonia and bleach. For painting and home repairs, it says birds should be moved far away from fumes, preferably to another location altogether.

AAV’s relocation sentence names painting and home repairs, not candles. No source cited here says how far candle smoke or scent travels, so the cautious course is our own judgment: keep the bird in a different room from any lit or scented candle.

AAV’s smoke paragraph adds that all smoke, from sources including engine exhaust, burning food and malfunctioning furnaces, can hurt a pet, and that symptoms may take several hours to appear. A bird that looks fine after smoke exposure may not be fine.

No source cited here names a wax, fragrance or product as safe around birds, so this page does not offer a bird-safe candle. AAV says a bird that has ingested any of the products it lists, or is acting ill, needs help immediately from an avian veterinarian. The bird-specific picture is in our bird and parrot page.

Improvisation three: dry ice

Dry ice enters an outage for a reason: a refrigerator full of medication or a freezer full of food. It is a real tool sold to consumers. This page does not say never to buy it. It says what dry ice turns into and where that gas goes.

What CGA publishes

CGA describes dry ice as extremely cold solid carbon dioxide that converts to gas at room temperature. It names the hazards as the extremely cold temperature, the potential to create an oxygen-deficient atmosphere, and rapid conversion from solid to gas. It says users must read and follow the instructions from their dry ice supplier.

• Storage. Store in cool, well ventilated areas. Ventilation systems should exhaust from the lowest level. Install carbon dioxide monitors and check concentration before entering a storage area. “NEVER store in airtight containers.”
• Transport. “NEVER transport in airtight containers.” Open windows or ensure a constant supply of fresh air in vehicles. In a passenger compartment or trunk, limit dry ice to small quantities and keep the windows open or fresh air flowing for the whole trip.
• Accumulation. Ventilate adjacent enclosed areas to prevent dangerous concentrations. “A concentration of 3% of carbon dioxide can be dangerous while higher concentrations can be lethal.” Rescue workers should not enter areas above 3% without a self-contained breathing apparatus or supplied-air respirator.
• Disposal. Let dry ice sublime in a well-ventilated area where no buildup of carbon dioxide vapor can occur.

Reading those rules as a pet owner

CGA never addresses animals, so the points below are this page’s reasoning applied to CGA’s rules.

• The car. If an animal is in the car, the rule gets stricter. A crated animal cannot move to the open window. Keep the quantity small, keep windows open, and never put a cooler of dry ice in a sealed trunk or cargo area that shares air with a carrier.
• The floor. This is the one place on this page where the low-animal intuition is correct. A crate on the floor, a rabbit in a hutch at ankle height, a tortoise table and a cat under a bed are all in the layer CGA designs exhaust for. CGA’s way to know whether a space qualifies is a carbon dioxide monitor, not a look at whether the room feels open. Never put dry ice in a closed room, closet, bathroom, garage or vehicle where an animal is confined.
• The container. The airtight rule exists because the gas needs somewhere to go. Sealing dry ice in a cooler and then putting the cooler in a closed vehicle or closed room turns one enclosure into two.
• Contact and swallowing. CGA says to use protective gloves or tongs and “NEVER handle with bare hands or place in mouth”. It says dry ice can freeze human tissue on contact, and that if swallowed it expands rapidly and can cause serious injury or death. Those warnings assume a reader who can choose. An animal cannot, so keep dry ice behind a closed, non-airtight lid the animal cannot open, and out of reach at all times, not only while it is subliming in the open. If a pet has touched dry ice or may have swallowed any, that is an emergency veterinary call, not a wait-and-watch.

The 5,000 ppm occupational limit is not a pet number

You may see 5,000 parts per million quoted for carbon dioxide. That figure is from OSHA’s Table Z-1 in 29 CFR 1910.1000, which also lists carbon monoxide at 50 ppm. The rule attached to it applies to an employee’s exposure and sets an 8-hour time-weighted average over a 40-hour work week. It is a limit on employer-controlled exposure for workers, not a line below which anyone is fine. It is not a threshold for a dog, cat, bird, rabbit or reptile, and a bird’s respiratory anatomy is not a mammal’s. Do not use it to decide whether a room is acceptable for an animal.

What is not published

The sources cited here give no carbon dioxide exposure threshold for companion animals; they publish human occupational values and human physiological effects. That is a statement about what these bodies publish, not a claim that no such figure exists anywhere. This page gives no pounds-per-cooler figure, sublimation rate, room ventilation rate or minimum room size for dry ice. Ask the dry ice supplier, whose instructions CGA says to follow, and your veterinarian for anything about the animal.

If you want dry ice for refrigerated medication, that decision has its own page: what the package inserts say about a warm refrigerator.

The three improvisations side by side

Improvisation	The hazard it creates	What the named sources publish	Substitute
Unvented heater, gas oven, camp stove, charcoal indoors	Carbon monoxide, plus nitrogen dioxide from kerosene per CPSC	ASHRAE: never the sole heat source, and consumers reducing exposure risk should not use unvented devices. CDC: never a gas oven for heat, never charcoal indoors, never a portable gas camp stove or flameless chemical heater indoors. CPSC: never fuel-burning heaters or lanterns while sleeping in enclosed areas	The sources cited here name no combustion substitute for heat. See the winter page for the non-combustion route
Candles for light	Fire, plus airway irritation for birds	NFPA and USFA: never use candles for outage lighting. NFPA 2020 to 2024: 5,894 home structure candle fires a year on average, over half from something flammable too close, sleep a factor in 34% of candle fire deaths. Merck and AAV: candles are on the airborne-hazard list for caged birds	Flashlights and battery-powered lighting, named by NFPA, USFA and the American Red Cross
Dry ice for cooling	Carbon dioxide buildup (about 1.5 times as heavy as air per CGA), plus freezing injury on contact and injury if swallowed	CGA: ventilated areas, never airtight containers, vehicle windows open, gloves or tongs, nothing in the mouth, follow the supplier’s instructions	None. CGA names conditions of use and the supplier as the person to ask

There is no swap for dry ice the way flashlights swap for candles, because it does a job nothing else in the house can do. That is why its rules are conditions rather than a replacement.

If an animal may have been exposed

No source cited here publishes a carbon monoxide or carbon dioxide level at which a pet is harmed, and none gives a clearance distance, room size or dry ice quantity for pet households. If you suspect exposure, the ASPCA says to take the animal to a local emergency veterinarian immediately. For anything about a specific animal, especially a bird or an animal with respiratory or heart disease, ask your veterinarian. For appliance questions, ask the manufacturer and your local building or fire department. For dry ice amounts, ask the supplier.

Your outage improvisation checklist

• Put battery-operated CO alarms, or alarms with battery backup, outside sleeping areas and on each floor, and test them monthly.
• Read the alarm’s installation instructions for mounting height and follow them. Do not mount an alarm low because an animal is low.
• Buy flashlights and battery lanterns before the season, and keep the batteries in the drawer.
• Decide now whether any unvented combustion appliance is part of your plan at all, and read ASHRAE’s positions before you decide, not in the middle of a cold night.
• If you own one, find its manual today and read the clearance, room and ventilation requirements while the lights are on. Call the manufacturer if the manual is gone.
• Call your local fire department’s non-emergency line once. Ask what your jurisdiction permits for unvented room heaters, and what number to call if a CO alarm sounds.
• Walk the room your household will use in an outage and identify every surface a cat can reach. If a flame would have to sit on one, it does not go in that room.
• If there is a bird in the house, plan its location away from any room where anything will be burned, scented or vaporized, and remember AAV’s advice to move birds far away from fumes.
• If anyone uses home oxygen, no candle enters the building. NFPA states it as an absolute.
• If dry ice is in your plan, ask the supplier for handling instructions, and rule out any closed room, closet, bathroom, garage or vehicle where an animal would be confined with it.
• Keep dry ice behind a closed, non-airtight lid an animal cannot open, out of reach at all times.
• Write down where each animal sleeps and where the crates and leashes are, so leaving fast does not require a search.
• Agree the human rule with everyone in the house: if a CO alarm sounds, everyone goes outside, calls 911, and nobody goes back in.

Where to go next

This page is the improvisation spoke of our outage playbook for pet households.

• The improvisation is outdoors: the generator page covers the machine that runs outside the house, including the alarm rules for the household it powers. Do not mix its placement figures with anything here.
• The animals are the constraint: the bird and parrot page covers the bird-specific side. Tanks and terrariums covers animals whose environment is the equipment. The fire plan covers the exit the alarm section assumes you can make.
• The season is the constraint: cold-weather preparation covers the non-combustion route to a warm room, and stored power sized to real loads covers the equipment that replaces a flame with a plug.

Then do the one thing that has to happen on a quiet afternoon: put fresh batteries in the CO alarms, put a flashlight in the room each animal sleeps in, and find the manual for whatever is in your garage.