Prices for carbon monoxide, natural gas, heat, duct, aspirating, and addressable detectors vary according to their features. Following are what some of the major manufacturers offer:

1. A carbon monoxide detector from CCI comes in either horizontal or vertical mount: $89.95.

2. A carbon monoxide detector from Silent Call flashes a 110-volt strobe light when activated, is hardwired, and offers a one-year warranty: $220.

3. A basic carbon monoxide detector from First Alert is hardwired: $40.

4. A voice combination smoke and carbon monoxide detector by Kidde is suitable for all living areas, has a voice alarm that designates fire or carbon monoxide, and a battery backup: $56.

5. A natural gas detector from RE Williams is hardwired with a battery backup, mute button, four indicator lights for alarm status, a five-year warranty, and an 85-decibel alarm: $69.

6. A natural gas/propane/butane detector from RE Williams does not connect to security systems but is hardwired and has a built-in sounder: $95.

7. A duct smoke detector from Nextag has photoelectric sensors with air velocities from 100 to 4000 FPM humidity and ambient temperature limits of 32 to 131 degrees F.: $150–$200.

8. A duct smoke detector from Firex is hardwired and has ionization sensors: $107.

9. A beam smoke detector by Fire Lite is photoelectric and addressable for protecting open areas with high and sloping ceilings: $917.

10. A dual-beam outdoor detector by Optex has photoelectric sensors, a low incidence of nuisance alarms caused by falling leaves, birds, blowing debris, and the like, and an anti-frost cover: $119.

11. A heat detector from General Electric has a 194-degree F. fixed temperature/rate-of-rise, is a single-circuit unit, and detects extreme changes in temperature (good for attics and kitchens): $12.

12. A heat detector with battery backup from Smoke Sign is hardwired with red and green LED lights: $32.50.

13. An addressable smoke detector from Fire Lite is hardwired, photoelectric, and the sensing chamber provides communication to provide open-air protection: $66.

14. An addressable duct detector from Fire Lite is photoelectric and has two LEDs on each detector: $216.

15. A 3-in-1 detector for carbon monoxide, propane, and natural gas from Nextag is hardwired and has two independent 85-decibel alarms: one sounds for CO and the other for propane and natural gas. This detector has a computerized calibration to help eliminate nuisance alarms and a built-in self-diagnostic to help ensure the unit is operating properly. It samples the air every 2 1/2 minutes and comes with a five-year warranty: $69.95.