No, a carbon monoxide detector will not detect a gas leak. A CO alarm senses carbon monoxide, a gas produced when fuel burns incompletely. Natural gas (methane) and propane are different gases, and a standard CO alarm does not respond to them. To be alerted to a natural gas or propane leak, you need an explosive or combustible gas alarm, or a combination unit that senses both.
- CO alarms sense carbon monoxide, not natural gas or propane.
- An explosive gas alarm, or a combo unit, is needed to sense gas leaks.
- Natural gas alarms mount high; propane alarms mount low.
- Smell gas? Leave first and call from outside, alarm or not.
Carbon Monoxide vs. Natural Gas
Carbon monoxide (CO) is a colorless, odorless gas created when fuel such as gas, propane, oil or wood burns without enough air. It comes from appliances that are running, like a furnace, water heater, range or generator, when they are faulty or poorly vented. It is a poisoning hazard.
Natural gas and propane are the fuels themselves. Utilities and suppliers add an odorant that smells like rotten eggs so a leak can be noticed. A leak is a fire and explosion hazard, and it can happen whether or not any appliance is running.
Because they are different gases, the sensors that detect them are different too.
Which Alarm Do You Need?
- CO alarm: for any home with fuel-burning appliances or an attached garage.
- Explosive gas alarm: for homes with natural gas or propane lines, as an extra layer beyond the rotten-egg smell.
- Combination unit: senses both CO and explosive gas in one device. Check the label to confirm which gases it detects.
Follow the manufacturer's instructions for placement and replacement, and test alarms regularly.
Where to Mount a Gas Alarm
Natural gas is lighter than air and rises, so natural gas alarms are usually mounted high on a wall or near the ceiling. Propane is heavier than air and settles, so propane alarms go low, near the floor. Many rural homes around Dover and Plant City use propane; see our propane safety guide.
If You Smell Gas
Safety first: If you smell gas or an alarm sounds, don't flip switches or use a phone inside. Get everyone out, then call your gas utility, propane supplier or 911 from outside.
An alarm is a backup, not a replacement for your nose. Know the other signs of a gas leak, such as hissing near a line or dead plants over a buried pipe.
After the Emergency: Testing the Lines
Once the utility or supplier has made the situation safe, a licensed provider can test the system to confirm it is tight. A gas line pressure test shows whether the piping holds pressure, and leak detection solution or an electronic detector finds the exact joint. Learn more on our gas line testing page.
Frequently Asked Questions
Can a carbon monoxide detector detect natural gas?
No. A standard CO alarm only senses carbon monoxide. It will not respond to natural gas or propane.
Is there one detector for both CO and gas leaks?
Yes, combination alarms that sense CO and explosive gas are sold. Check the packaging to confirm both are listed.
Why didn't my CO alarm go off when I smelled gas?
Because it isn't designed to. Treat the smell as a leak: leave the home and call from outside.
Should a propane alarm go high or low?
Low, since propane is heavier than air. Natural gas alarms go high.
Who tests my gas lines after a leak?
A licensed provider. Call (813) 303-9621 to be connected with a local provider, and get a free quote for line testing.
