HVAC after-hours calls: no heat, no AC, and what can wait until morning

Sort every HVAC call after hours into one of three piles. Get out and call 911: a gas smell, a carbon monoxide alarm or symptoms, smoke or fire. Send someone tonight: no heat or no cooling with someone at risk in the house or the weather past the line you set, or water from the equipment that won't stop. First slot tomorrow: the system runs but not well, one room is off, a new noise, or anything that's really a maintenance or estimate call.

Whoever answers at night (you, an answering service or an AI receptionist) asks the safety questions first, then a few about the system, then sorts the call by rules you wrote down in daylight. Below: the script, a fill-in on-call rules table, and what to tell the caller who waits until morning.

1. The safety questions come before anything else

Ask them on every call, even when the caller only says “my furnace stopped”:

• “Do you smell gas?” If yes, they hang up, leave the house now and call from outside. The U.S. Consumer Product Safety Commission says to leave immediately, contact local gas authorities from outside the home, and not operate any electronics, such as lights or phones, before leaving (CPSC winter safety tips). Don't book anything until the gas utility or fire department has been out.
• “Is a carbon monoxide alarm going off, or does anyone feel sick, dizzy or have a headache?” CPSC's advice if you suspect CO poisoning is to get outside to fresh air immediately and then call 911 (CPSC carbon monoxide center). The CDC lists the common symptoms as headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion, and calls them “flu-like” (CDC). A family that all has the flu on the night the furnace acts up is a CO question, not a scheduling question.
• “Any smoke, sparks or burning smell from the unit or the thermostat?” Smoke or fire means everyone gets out and calls 911 or the fire department (Ready.gov home fires). A burning smell with no smoke is your call to make in advance: write down whether it goes to your on-call tech tonight or the first slot, and have the caller switch the system off at the thermostat meanwhile.

Write the answer to each one down and keep it word for word: “Please hang up now, leave the house, and call 911 or your gas utility from outside. Don't switch lights or anything else on or off on the way out.” Nobody should be making up a safety answer at 10 PM.

2. “Is it no heat, no cooling, or something else?”

Once safety is clear, find out what kind of call it is. Three answers cover most nights:

• No heat at all: furnace, heat pump or boiler not running, or blowing cold air.
• No cooling at all: AC not running, or running and blowing warm air.
• Something else: it runs but the house won't get to temperature, one room is cold, a new noise, water near the unit, or the thermostat screen is blank.

The quick questions before you book

These aren't a repair over the phone. They tell your tech what to expect, and now and then they solve the call. Only ask what the caller can check safely from where they are.

1. “What does the thermostat say?” Is it set to heat (or cool), is the set temperature above (or below) the room, and is the screen on? A blank screen can mean dead batteries or no power to the system, and your tech wants to know either way.
2. “When was the filter last changed?” Just note the answer. If they're not sure, the tech will look.
3. “Is water coming from the indoor unit or through a ceiling?” If yes, ask them to switch the system off at the thermostat and put down towels or a bucket, and move this call up your list.

Leave breakers, gas valves and furnace panels to your tech. If the caller mentions a tripped breaker, write it down for the tech rather than walking them through the panel at night.

3. “Who's in the house tonight?”

For a no-heat or no-cooling call, the answer to this question decides most of whether it waits. The CDC names the people at higher risk from heat as adults 65 and older, babies and young kids, people with ongoing health conditions, pregnant people and people without air conditioning (CDC: people at increased risk for heat-related illness). For cold, it names older adults without proper heating and babies sleeping in cold rooms among the high-risk groups (CDC winter weather).

Ask it plainly: “Is anyone in the house elderly, a baby, or someone with a medical condition?” If anyone has a headache, dizziness or nausea, go back to the carbon monoxide question in step 1.

4. Your on-call rules, on one table

The person answering shouldn't be deciding whether to wake your on-call tech. You should, once, in writing. Copy this table, fill in your own numbers and choices, and give it to whoever covers your phone. The middle column is a starting point many small shops would recognize, not a rule from anyone; change it to fit your area, your fees and how many techs you have on call.

The temperature lines matter most. Pick numbers for your climate and use them every night, so a mild-night thermostat question doesn't get your tech out of bed and a no-heat call from a house with a newborn doesn't wait until Thursday.

5. What to tell the caller who has to wait until morning

The caller who has to wait also wants to know how to get through the night safely. Stick to official advice:

• Never heat the house with a gas oven. The CDC says so directly (CDC carbon monoxide).
• Space heaters: keep every side at least three feet from beds, clothes, curtains, papers and sofas (CPSC).
• Generators stay outside: never in the house or garage, even with doors and windows open, and at least 20 feet from the home with the exhaust pointed away (CPSC).
• If anyone gets a headache, dizziness or an upset stomach during the night, treat it as possible carbon monoxide, since those are common CO symptoms (CDC): get outside to fresh air, then call 911 (CPSC).

Then confirm the slot: “You're first on the list for 8 to 10 tomorrow morning. If anything changes tonight, call us back on this number.”

6. The address, the number and the way in

Take the full address with any unit number or gate code, and the name and best number, and read both back. Then the HVAC extra: where is the equipment (attic, crawlspace, closet, roof, side yard), and is there a dog or a locked gate? More on the read-back in after-hours calls for plumbers; the same steps work for HVAC.

7. Say the after-hours fee the same way every time

If you charge an after-hours or emergency trip fee, the person answering should say it word for word before booking: “Our after-hours service fee is [your exact fee], and the tech will quote any repair before starting work.” Anything else about price gets the same answer: the tech quotes on site. A caller who heard the fee on the phone is less likely to argue about it at the door.

The script on one page

1. “Thanks for calling [your company]. How can I help?”
2. “Before anything else: do you smell gas, is a carbon monoxide alarm going off, or does anyone feel sick or dizzy?” (Yes: “Please hang up, leave the house now, and call 911 or your gas utility from outside.”)
3. “Any smoke, sparks or burning smell?” (Smoke or fire: everyone out, call 911. Burning smell only: your rule.)
4. “Is it no heat, no cooling, or something else?”
5. “What does the thermostat say? Is the screen on, and is it set to heat (or cool)?”
6. “Is any water coming from the unit or through a ceiling?” (Yes: switch it off at the thermostat and catch the water.)
7. “Is anyone in the house elderly, a baby, or someone with a medical condition?”
8. Check your rules table: on-call tonight, first slot tomorrow, or regular booking.
9. “What's the address, with any unit number or gate code?” Read it back. “Where's the equipment?”
10. “Your name and the best number to reach you?” Read the number back digit by digit.
11. “Our after-hours fee is [your exact fee]. I can get someone out [tonight between X and Y / tomorrow between X and Y]. Does that work?”
12. Waiting until morning: the oven, space heater, generator and CO lines from section 5 (sources: CDC, CPSC), then “If anything changes tonight, call us back.”

Busy nights: the first cold snap and the first heat wave

HVAC calls come in bunches. The first properly cold night or the first hot week can bring a pile of no-heat or no-cooling calls at once. Three things help:

• Decide your on-call limit before the night comes. How many night visits can one tech do? Once they're full, the table still sorts every call, and the rest go into tomorrow's first slots in order: at-risk households first.
• Decide who goes when the list is full and an at-risk household calls. A second tech, or you. Write the name down now, not at midnight.
• Keep answering. On a surge night the caller who can't get through rings the next shop. A booked 7 AM slot is more likely to keep the job than a voicemail.

For the week-before prep (tune-ups, parts, the on-call rota, a surge-day triage order and what to say when you can't get there today), see our first cold snap checklist.

If you're pricing what it costs to cover those nights, our AI receptionist cost guide works through a 50-call month for a plumbing or HVAC shop, with every price sourced.

Who answers your phone at 10 PM?

For a lot of owner-run shops it's the owner, if they hear it. The other choices are voicemail, a live answering service or an AI receptionist, and we compare them in AI receptionist vs answering service vs voicemail. If you're thinking about hiring for it, see HVAC dispatcher or answering service for what each really costs.

Voxlivo is the after-hours and overflow line for HVAC and plumbing shops. It picks up in your company's name, says it's a virtual assistant and that the call may be recorded, tells anyone who mentions gas, fire or flooding to hang up and call 911, takes the address, number and what's wrong, says your after-hours fee word for word, books the job into your Google Calendar and emails you a summary (if you run your jobs in other software, the details arrive by email instead). A person writes your script from your own rules, and you hear it before it goes live: ask for the CO and who's-in-the-house questions to be in yours, and check them when you listen. On Growth and above it can put a real emergency straight through to your on-call phone. On Starter it doesn't ring anyone: the email summary reaches you within about a minute and you decide whether to send your tech. You keep your number and forward only the calls you can't take, or everything after closing (how to forward your calls).

Starter is $49 a month for 100 minutes, and Growth is $99 a month for 200 minutes (see pricing). See how it handles heating and cooling calls on our answering service for HVAC companies page, or read about after-hours answering.

Questions owners ask

Is no heat an emergency?

It depends on who is in the house and how cold it is. A house with a baby or an elderly person on a freezing night is a tonight call for most shops. Healthy adults on a mild night can usually wait for the first slot. Write your temperature line into the rules table so it's the same answer every time.

Is no AC an emergency?

Ask the same two things: who is in the house, and how hot it is. The CDC lists older adults, babies and young kids, people with ongoing health conditions, pregnant people and people without air conditioning as being at higher risk in the heat (CDC). Set your outside-temperature line, and treat at-risk households as tonight calls.

Should whoever answers try to fix it over the phone?

No. Asking about the thermostat, the filter and any water is fine, and it tells your tech what to bring. Breakers, gas valves and furnace panels wait for the tech.

What if the on-call tech doesn't pick up?

Put a backup in your rules: a second number to try, and what to tell the caller if nobody answers in time (for example, the first slot tomorrow, booked now). Decide it in daylight, like the rest of the table.

What should they say if the caller smells gas?

“Please hang up now, leave the house, and call 911 or your gas utility from outside. Don't switch lights or anything else on or off on the way out.” That follows CPSC's advice to leave immediately, call from outside and not operate lights or phones before leaving (CPSC). Then book only once the utility or fire department has made it safe.

Sources checked 4 November 2026: CPSC winter weather safety tips · CPSC Carbon Monoxide Information Center · CDC: about carbon monoxide poisoning · CDC: people at increased risk for heat-related illness · CDC: preventing cold-related illness · Ready.gov: home fires.