Smoke and carbon monoxide detectors are two different tools doing two different jobs, and Chicago and Illinois both have specific rules about where each one belongs. Here's what the different smoke detector types actually detect, where the law requires them, and when you need a CO detector too.
The different types of smoke detectors
- Ionization alarms. More sensitive to the small smoke particles produced by fast-flaming fires, like a grease fire or a paper fire that spreads quickly.
- Photoelectric alarms. Better at catching the larger smoke particles from slow, smoldering fires, like a cigarette smoldering in upholstery for hours before it ignites.
- Dual-sensor (combination) alarms. Combine both technologies in a single unit, since a real house fire can start either way. This is generally the safest single option if you'd rather not install two separate alarm types.
Where Chicago requires smoke alarms
- In homes built or substantially remodeled before 2018: outside and within 15 feet of each bedroom
- In homes built or remodeled in 2018 or later: both inside each bedroom and outside within 15 feet
- At least one alarm on every level of the home, including the basement
- Not within 10 feet of a cooking appliance for ionization alarms, or 6 feet for photoelectric alarms
- Not within 3 feet of a bathroom door, and not within 4 inches of a wall-ceiling corner
The sealed 10-year battery rule
Illinois law phased out removable-battery smoke alarms: installing a new one became illegal as of January 1, 2023. Homes still relying on older removable-battery alarms need to switch to sealed-battery or hardwired units by January 1, 2033. Regardless of type, every smoke alarm should be replaced after 10 years of use, check the manufacture date printed on the back of the unit if you're not sure how old yours is.
When and where you need a CO detector
Illinois law requires a carbon monoxide detector in any home that uses fossil fuels, natural gas, propane, oil, for heating, cooking, or hot water, or that connects to an enclosed or attached garage. In practice, that covers the vast majority of Chicago homes.
- Install within 15 feet of every room used for sleeping, following the manufacturer's specific instructions
- Avoid placing it in the kitchen, the garage, or right next to the furnace, those locations can cause false alarms or reduce accuracy
- Look for certification from a recognized testing laboratory (UL or CSA) when buying one
Why it matters at the point of sale
Smoke and CO detector compliance is a common item inspectors and appraisers check during a real estate transaction. If you're getting ready to list, or you've just moved into an older home, it's worth a quick walk-through to confirm every alarm is the right type, in the right spot, and within its 10-year lifespan.
