A carbon monoxide alarm going off means one thing: get everyone out now, pets included. Call 911 from the driveway, not from the kitchen. Do not open windows on the way out, because fresh air erases the reading the fire department needs. After they clear the house, call 631-591-2289 and we will find the source.
If the Alarm Is Going Off Right Now
Follow these steps in order. Skip nothing.
Get everyone outside, pets included. Carbon monoxide has no smell and no color. You cannot judge the danger by how you feel, because CO dulls your thinking as it builds. Dogs and cats are hit even faster than people. Head straight out the nearest door.
Do not open windows first. This is the step most people get wrong. Airing out the house drops the CO level before the fire department arrives with their meters. A zero reading means they cannot confirm the leak or trace it. Leave the air alone and just walk out.
Call 911 from outside. Firefighters carry meters that read CO in parts per million. They will check every room and tell you the peak number. That number is the single best clue for finding the source later, so ask for it and write it down.
Stay out until they clear the house. Do not go back for phones or coats. A house that feels fine can still hold a dangerous level, because your nose gives you no warning at all.
Watch for symptoms. The classic signs are headache and nausea, along with dizziness and confusion. The tell is a whole family feeling sick in the same rooms at the same time, then feeling better outside. Tell the EMS crew if anyone has these signs, because CO poisoning is treated with oxygen and time matters.
After the Fire Department Clears the House
Clearing the house means the air is safe to breathe right now. It does not mean the source is fixed. Here is what to do next, and none of it involves opening up equipment yourself.
1. Keep the suspect equipment off (1 minute). If the crew pointed at the furnace, the boiler, or the water heater, leave it off until a technician tests it. Electric space heaters can bridge a cold night safely. Never use the oven for heat, and never run a generator indoors or in the garage.
2. Ask for the meter reading (2 minutes). Get the peak parts-per-million number and where in the house it was highest. A high reading near the utility room points at heating equipment. A high reading near the garage points at a vehicle or stored engine. That one number can save a technician an hour of hunting.
3. Book a combustion inspection (10 minutes). Call and tell us the alarm went off and the house has been cleared. We test every fuel-burning appliance with a combustion analyzer, not a guess. This is a same-day call for us, any day of the week.
4. Check the date on the back of each alarm (5 minutes). Every CO alarm has a replacement date printed on the back, and the sensor inside dies after 5 to 10 years. An expired unit can false alarm, and worse, it can fail silent. Replace any unit past its date today.
5. Write down what was running (5 minutes). Note what was on when the alarm sounded: the heat, the water heater, the oven, a car warming up, a generator. Matching the timing to the equipment narrows the search fast. Bring the list to the technician.
What a Carbon Monoxide Alarm Going Off Usually Means
Not every sound from the unit is an emergency. The pattern tells you which problem you have.
| Symptom | Likely cause | Urgency |
|---|---|---|
| Four quick beeps, a pause, then four more, repeating | CO detected | Get out, call 911 now |
| One chirp every 30 to 60 seconds | Low battery | Swap the battery today |
| Chirps in a fixed pattern, often with a yellow or blinking light | End of life, the sensor is expired | Replace the unit today |
| Alarm sounding while everyone in the room feels sick or dizzy | Active CO exposure | 911 from outside, now |
| Alarm sounded, then stopped on its own | Possible low-level event | Have the equipment tested today |
The full alarm is loud and steady, the kind of sound you cannot sleep through. A chirp is a single short beep with a long gap. People die every year because a real alarm was written off as a dying battery, so when in doubt, treat it as real and get out.
Call Now or Can It Wait
Call 911 first, then us, any hour:
- The repeating four-beep alarm pattern is sounding
- Anyone in the house has a headache, feels queasy, or seems confused
- Symptoms ease outside and come back indoors
- The alarm sounds again after the fire department left
- A car, a grill, or a generator was running in or near the garage
It can wait for a daytime appointment:
- A single chirp every 30 to 60 seconds and a fresh battery fixes it
- The unit is past the replacement date on the back and needs swapping
- You want a combustion safety check before heating season starts
- You added new alarms and want the placement looked over
Where the Carbon Monoxide Comes From
CO is unburned fuel exhaust that ended up inside the house instead of outside it. In our service calls, the source is almost always one of five things.
A cracked heat exchanger
The heat exchanger is the metal wall between the flame and the air blowing into your rooms. Decades of heating and cooling cycles can crack it, and a crack lets exhaust leak into the supply air. This is the most serious furnace failure there is, and it usually means replacement.
A blocked or rusted flue
The flue carries exhaust up and out. Bird nests, fallen leaves, crumbling chimney liner, and rust flakes can choke it over a single summer. When the exhaust cannot get out, it spills back into the basement.
Backdrafting in a tight house
Modern sealed windows and doors make a house tight. Run a big kitchen exhaust fan, a couple of bathroom fans, and the dryer at once, and the house can go negative. That suction can pull exhaust back down the flue of a water heater or boiler. The equipment is healthy, yet the alarm still goes off.
A sooted-up oil burner
Oil heat is everywhere in our area, and an oil burner that skipped its annual cleaning burns dirty. Soot builds in the chamber and the flue, the flame starves for air, and CO output climbs. A smoky or rumbling burner should be checked before it ever trips an alarm.
Engines: cars and generators
A car idling in an attached garage can push CO into the house within minutes, even with the garage door open. Portable generators are the storm-season version of the same mistake. A generator belongs outside, at least 20 feet from the house, with the exhaust aimed away from windows.
Detector Placement and the Date on the Back
You need a CO alarm on every level of the home and outside each sleeping area. Put one within earshot of every bedroom door, because most CO deaths happen during sleep. Keep alarms at least 15 feet from the furnace, the stove, and any fuel-burning appliance to avoid nuisance trips. Do not mount one inside the garage itself.
Then flip each unit over and read the date. Manufacturers print the replacement date on the back, and the sensor is done after 5 to 10 years no matter how new it looks. The test button only proves the horn and circuit work, not the sensor. If there is no date at all, the unit is old enough to replace on the spot.
What We Do When We Arrive
The technician starts with your notes: the meter reading, where it peaked, and what was running. Then we test each fuel-burning appliance one at a time with a combustion analyzer, which reads the CO in the exhaust as the equipment runs. We check the flue for draft and blockage, inspect the heat exchanger, and watch for backdrafting with your exhaust fans running. The source shows up in the numbers, not in guesswork.
You get the findings in plain English and any repair priced in writing before we touch a part. If the equipment is safe to run, we tell you that too. Either way you sleep that night knowing, instead of wondering.
What Finding the Source Costs
The combustion inspection is part of our standard $189 service call once the fire department has cleared the home, and it includes the diagnosis and the first hour of labor. Parts are extra and priced in writing before install. After-hours calls are $249. A major repair, such as a flue rebuild or a burner overhaul, runs $500 to $950 on average.
A cracked heat exchanger on equipment 15 or more years old usually fails our 50 percent rule, where a repair quote over half the cost of replacement means we advise replacing. We show you both numbers and you decide.
House Cleared and Need the Source Found?
Same-day combustion inspections across Suffolk and Nassau through our heating repair team, $189 including diagnosis and the first hour of labor.
Call 631-591-2289Why CO Calls Spike Every Fall on Long Island
Our CO calls jump the first cold week of fall, every single year. That is the week thousands of burners fire for the first time in months, pushing a summer of rust flakes, spider webs, and nest debris into flues all at once. Oil heat makes it sharper here, since a burner that sat since April can start up sooty and stay that way. Pre-1960s homes in Nassau and western Suffolk add old masonry chimneys with crumbling clay liners that shed into the flue.
The shoreline adds its own problem, because salt air eats flue pipes and chimney caps from the outside in. Storm season overlaps all of it. After a PSEG outage, portable generators come out across the Island, and every year some end up in garages and breezeways. If your generator ran anywhere near the house during the last outage, take the alarm seriously even if the heat checks out clean.
If your CO alarm is sounding, if you smell gas, or if you see smoke, get everyone out first. Call 911 and National Grid from outside. Call us after the utility and fire department have made the house safe.