What Counts as an HVAC Emergency?

When your furnace stops on a January night or your AC dies during a July heat wave, every HVAC problem can feel like an emergency. Some truly are. Others are urgent but can safely wait until morning, and some are minor issues you may be able to fix yourself. Knowing the difference helps you act quickly when lives or property are at risk, and avoid paying after-hours rates when you do not need to.

This guide sorts common HVAC problems into three groups: life-safety emergencies that need 911 or the gas company first, HVAC emergencies that need prompt service, and problems that can wait. For urgent help, see how emergency HVAC service works.

Life-Safety Emergencies: Get Out First

These situations involve immediate danger. Your first call is not an HVAC company.

You Smell Gas

Natural gas is treated with an odorant that smells like rotten eggs or sulfur. If you smell it:

• Leave the building immediately with everyone, including pets.
• Do not turn lights, appliances or the thermostat on or off, and do not use phones inside. Any spark could ignite gas.
• Do not try to find the leak.
• Call Peoples Gas at 866-556-6002 or 911 from outside or from a neighbor's home.

Our guide on what to do if you smell gas near your furnace covers this in detail.

Your Carbon Monoxide Alarm Sounds

Carbon monoxide has no smell. If a CO alarm goes off, get everyone outside to fresh air and call 911. Do not go back inside until responders say it is safe, and do not use the furnace, boiler or water heater until they have been inspected. Our carbon monoxide safety guide has more.

Smoke, Fire or a Strong Burning Smell

If you see smoke or flames from HVAC equipment, or a strong electrical burning smell continues, get everyone out and call 911. If it is safe to do so on the way out, turn off the equipment's power switch.

Someone Shows Signs of Heat Illness or Hypothermia

If someone is confused, unresponsive, has a very high body temperature, or shows signs of severe cold exposure, call 911. Medical needs come before HVAC repairs.

HVAC Emergencies: Call for Prompt Service

No Heat in Freezing Weather

No heat is an emergency when outdoor temperatures are near or below freezing, the house is cooling quickly, and especially when:

• Infants, older adults or people with health conditions live in the home.
• Pipes are at risk of freezing.
• There is no safe backup heat.

Before calling, check the basics: thermostat, power switch, breaker, filter and outdoor vent pipes. Our furnace won't turn on checklist walks through them. If heat does not return, call. For steps while you wait, see no heat at night: safe steps until help arrives.

No Cooling During Extreme Heat

A failed AC during a heat wave can be dangerous, especially for older adults, young children, pregnant people and anyone with heart, lung or other health conditions. If the indoor temperature is climbing to unsafe levels and vulnerable people are present, treat it as an emergency. See AC out in a Chicago heat wave.

Water Leaking Near Electrical Equipment

Water pouring from an AC, furnace or boiler near wiring, outlets or electrical panels is a hazard. Turn off the equipment at the switch or breaker if you can do so safely, and call for service.

Repeated Breaker Trips

A breaker that trips again immediately after a reset points to an electrical fault. Leave it off and call for service.

Boiler Problems in Cold Weather

A boiler that has lost water, is leaking significantly, or has a relief valve discharging hot water or steam needs prompt attention. A steam boiler that is hot with no water in the sight glass should be turned off and left to cool. Do not add water. See our guide on boiler on but no heat.

Frozen or Bursting Pipes Because Heat Failed

If heat fails and pipes freeze or burst, shut off the main water valve if water is flowing, call a plumber for the pipes and an HVAC company for the heat.

Urgent but Usually Can Wait Until Morning

These problems need attention soon, but often not in the middle of the night:

• No heat on a mild night when the house is holding a safe temperature.
• No AC on a moderate day without vulnerable occupants.
• Uneven heating or cooling.
• Strange but not alarming noises, such as a squeal or rattle without burning smells.
• A small water leak contained by towels or a pan, away from electrical components.
• A thermostat that is acting oddly but the system still runs.
• Higher than usual energy bills.

Call during business hours. If things get worse, such as the house getting too cold or a smell developing, re-evaluate.

Problems You Can Often Fix Yourself

• Thermostat set to the wrong mode or with dead batteries.
• Furnace or AC power switch turned off.
• A tripped breaker that resets and stays on.
• A clogged filter.
• Snow blocking high-efficiency furnace vent pipes.
• Closed registers or blocked returns.
• A clogged condensate line you can clear with a wet-dry vacuum.

Our guides on AC won't turn on and AC leaking water walk through these.

How to Decide Quickly

• Is there a gas smell, CO alarm, smoke or fire? Get out and call 911 or Peoples Gas.
• Is anyone in danger from the indoor temperature? Treat it as an emergency.
• Is property at risk, such as freezing pipes or water near electrical equipment? Call promptly.
• Is the home safe and stable? It can probably wait for regular hours.

What to Tell the HVAC Company

• Your address and best phone number.
• The type of system: furnace, boiler, heat pump, AC or mini-split.
• What is happening: no heat, no cooling, noise, leak, smell.
• Any error codes or blinking lights.
• The current indoor temperature.
• Who is in the home, especially vulnerable people.
• What you have already checked.

Renters: Notify Your Landlord

If you rent, notify your landlord or property manager immediately about heating or cooling failures. In Chicago, landlords must provide heat during the heat season. See our guide on Chicago heat rules for landlords and tenants. For gas leaks or CO alarms, call the gas company or 911 first, then the landlord.

Prevent Emergencies Before They Start

Many emergency calls are preventable with seasonal maintenance. A fall furnace or boiler tune-up and a spring AC tune-up catch failing parts before they quit during extreme weather. See our fall furnace checklist, spring AC checklist and tune-up page.

Emergency vs. Urgent: Real-World Examples

Example 1: January, 5 Degrees, Furnace Silent

A family with a newborn wakes to a 60-degree house that is still dropping. The thermostat is on, the breaker is fine, the filter is clean and the outdoor vent pipes are clear, but the furnace shows a lockout code. This is an emergency. Call for service, keep everyone in one warm room using safe heat, and protect pipes.

Example 2: October, 55 Degrees, No Heat

The furnace will not start on a mild autumn evening. The house is 66 degrees and holding, and nobody in the home is especially vulnerable. This is urgent but can likely wait for a next-day appointment. Check the basics, use extra blankets and call in the morning.

Example 3: July Heat Wave, AC Out, Older Parent at Home

The AC fails during a heat advisory. Upstairs bedrooms are climbing past 85 degrees, and an older parent lives in the home. Treat it as an emergency. Call for service, move to the coolest part of the house, and plan to go to an air-conditioned place if temperatures keep rising.

Example 4: Water Dripping From the AC in May

A slow drip from the indoor unit onto a basement floor, away from electrical equipment, can usually wait for regular hours. Turn the AC off, catch the water and clear the drain if you can. If water is reaching outlets, a ceiling below or the furnace controls, call promptly.

Why Response Times Stretch in Extreme Weather

During polar vortex events and heat waves, HVAC companies receive far more calls than usual. Most prioritize situations involving safety, vulnerable occupants and risk of property damage. Giving clear information when you call helps the company triage correctly. It also helps to call as soon as you notice a problem rather than waiting to see if it resolves, especially when temperatures are extreme.

Have Your Information Ready Before Winter

Write down your furnace or boiler make and model, the filter size, the location of the service switch, breaker and gas shutoff, and your HVAC company's number. Keep it somewhere everyone in the household can find it. When something goes wrong at night, you will not have to search for details while the house cools.

Emergency Calls in Multi-Unit Buildings

In two-flats and apartment buildings, heating and cooling failures often affect several households at once. Tenants should notify the landlord or manager immediately, and owners should have an emergency HVAC contact ready. If a shared boiler fails during heat season, the situation is urgent for every unit and may also have legal implications under the city's heat ordinance.

When Not to Wait

It can be tempting to wait until morning to avoid after-hours rates, and in many cases that is reasonable. But do not wait if the house is losing heat quickly in freezing weather, if pipes are at risk, if someone in the home is vulnerable to cold or heat, or if anything smells like gas, smoke or burning. The cost of frozen pipes, water damage or a medical emergency far outweighs the cost of an emergency service call.

Keep an Emergency Kit Near the Furnace

A small kit makes nighttime problems easier to handle: a flashlight, spare filters, thermostat batteries, a notepad for error codes, your HVAC company's number and the Peoples Gas emergency number. Keep it near the furnace or boiler so you are not searching in the dark.

Need Help Now?

If you are facing an HVAC emergency and everyone is safe, call (312) 638-0812. We serve neighborhoods across Chicago including Uptown, Humboldt Park and River North.