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  • 2-in-1 Carbon Monoxide and Natural Gas Smart Alarm
  • 120 Volt AC Hardwired Alarm
  • Can be used to replace the USI-7390 alarm, uses same connector plug.
  • Dual Technology Offers Double Protection
  • 9 Volt Eveready Alkaline Battery Backup Included
  • Loud 85 dB Alarm
  • Self Diagnostic Feature
  • Product End of Service Life Warning
  • Test/Reset Button
  • Quick Draw Battery Drawer
  • 3 LED's Indicate: Power, CO & Gas
  • Interconnectable up to 24 Compatible Devices
  • Quick Find Alarm Origination/Locator
  • Tamper Resistant Locking Feature for Alarm & Battery
  • Battery Activation Pull Tab
  • Bracket Mounts to any Standard Wiring Junction Box
  • Ideal for Homes, Apartments and Mobile Homes
  • Conforms to UL Std. UL 2034 and UL 1484
  • California State Fire Marshal Approved
  • 7 Year Limited Warranty
The USI Electric MCN108 Hardwired Carbon Monoxide and Natural Gas Smart Alarm is a 2-in-1 device that provides double the protection with a single installation. This dual-sensing alarm protects against two deadly household threats: carbon monoxide and natural gas (or methane). Perfect for new or replacement installations, the 120-volt AC/DC hardwired alarm is suitable for houses, apartments and mobile homes. Auto sensitivity calibration provides superior nuisance alarm protection and creates consistency in alarm sensitivity. This alarm has additional automatic features including a self-diagnostics check to ensure proper operation, a sensitivity adjustment for changes in temperature or humidity and an end-of-service life warning that sounds when it's time to replace the battery. The 9-volt alkaline battery (included) continues protection in the event of a power outage.

This alarm features a quick activation pull-tab and a front-loading battery drawer for replacement without removing the alarm from the bracket. Mount the bracket to any standard wiring junction box and use the large mounting base to cover imperfections in drywall. The plastic dust cover protects the alarm from debris and (2) tamper-resistant locks prevent unwanted alarm or battery removal. For maximum protection, install an alarm inside every bedroom, outside every sleeping area and on all levels of the dwelling. The USI Electric MCN108 Hardwired Carbon Monoxide and Natural Gas Smart Alarm comes with a 7 year limited warranty.
Carbon monoxide alarms are designed to alarm before the average healthy adult feels symptoms. Since you cannot see or smell CO, never assume it's not present. Underwriters Laboratories Inc. Standard UL2034 requires residential CO alarms to sound when exposure times and exposure levels of CO in the chart below. CO alarm levels are measured in parts per million (ppm) of CO over time (in minutes). The UL2034 Required Alarm Points are:
  • If the Alarm is exposed to 400 ppm of CO, it must alarm between 4 and 15 minutes.
  • If the Alarm is exposed to 150 ppm of CO, it must alarm between 10 and 50 minutes.
  • If the Alarm is exposed to 70 ppm of CO, it must alarm between 60 and 240 minutes.
Carbon monoxide is not heavier than air. A carbon monoxide alarm should be installed in a location where the alarm will stay clean, and out of the way of children or pets. Refer to the user's manual for specific installation requirements.
It is very important to install a carbon monoxide alarm outside each separate sleeping area, and for maximum protection, install one in every bedroom. Many states now require installation of a carbon monoxide alarm inside each bedroom. For added protection, placement of an additional carbon monoxide alarm at least 15-20 feet away from the furnace or fuel burning heat sources is recommended. Install carbon monoxide alarms a minimum of 10 feet from sources of humidity like bathrooms and showers. In multiple-story dwellings, install one carbon monoxide alarm on every level. If you have a basement, install a carbon monoxide alarm at the top of the basement stairs, and in each separate sleeping area.
Do not install carbon monoxide alarms in garages, kitchens, furnace rooms, or in any extremely dusty, dirty, humid, or greasy areas. Do not install alarms in direct sunlight, or areas subjected to temperature extremes. These areas include unconditioned crawl spaces, unfinished attics, un-insulated or poorly insulated ceilings, and porches. Carbon monoxide alarms should not be installed in outlets covered by curtains, heavy furniture or other obstructions. Do not install in turbulent air-near ceiling fans, heat vents, air conditioners, fresh air returns, or open windows. Blowing air may prevent carbon monoxide from reaching the CO sensors.
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USI Electric Hardwired 2-in-1 CO and Natural Gas Alarm, Battery Backup Video

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MCN108 customer reviews

Overall Rating

70 Reviews
69 customers recommend this product
USI Electric Hardwired 2-in-1 CO and Natural Gas Alarm, Battery Backup Reviews
Michael H
October 28, 2022
Verified Purchase

Delivery was on time and they had the product that I needed.

Michael H
October 26, 2022
Verified Purchase

Delivery was on time and they had the product that I needed.

Stephen M
August 18, 2022
Verified Purchase

Easy to install. No programming required. Simple read out

Barry S
July 16, 2022
Verified Purchase
CO and Natural Gas Detector

Item performed as stated

Helen B
June 16, 2022
Verified Purchase


David L
February 27, 2022
Verified Purchase
USI Electric Carbon Monoxide and Natural Gas

This alarm replaced my previous hard-wired USI Carbon Monoxide alarm. It was reasonably priced and delivered to my home on time. It was very easy to install as the electrical connector was the same as my previous model. It also detects Natural Gas as an added bonus. Overall, I am very pleased with this purchase and would recommend it.

Alberto N
December 31, 2021
Verified Purchase
Good Experience

Good experience ordering on website. Delivery of product and product itself.

Kris J
November 17, 2021
Verified Purchase
Good product

Product works great

Ross K
November 9, 2021
Verified Purchase
Smoke replacement

I was pleasantly surprised this company was still producing after there product has been in homes.for 10 years. Thanks for providing me a 1 for 1 swap option you saved me a lot of time.

James D
October 21, 2021
Verified Purchase
USI Product and Service

Typical quality product from USI, with a good selection of options and ease of installation. I continue to purchase from Universal because of their excellent customer service, very prompt order fulfillment and shipping.

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