Review on Fast Low-Level Carbon Monoxide (CO) Detector for Cars, Vehicles, and Aircraft - 9ppm Alarm, Ideal for Police, Pilots, Travel, Buses, and Trucks, Compact Metal Body (2oz) by Brent Shaeffer

***Update*** I was contacted by Forensics (the seller) after I posted my review. They informed me that their return policy is actually one year and not 90 days on the Amazon profile. Replacing the battery did not completely fix the problem with the device. The seller replaced it quickly and free of charge. It will be a few months before I have to change the batteries in a new device, it will be some time before I can test it. However, due to the seller's actions and willingness to endorse their product, I have updated my review. If the second device continues to work after the battery change, I would give the product and seller 5 stars, but 4 stars for now. I would be confident in purchasing other items from this seller. I bought it on September 30th, 2018 and it arrived quickly with Prime. Yesterday I noticed the battery level was very low and today the screen was off. I bought and installed a new battery. Then I calibrated the device. I usually keep it in my car, but after putting the battery in I left it on the table in the living room. About five hours later (we were in bed) the alarm clock rang. I got up and the device registered readings from 12 to 26. There is another monitor in the same room plugged into the outlet, its reading is zero. I connected an extra unit in the bedroom that also reads zero. I don't know why this blockage started to bother me and I couldn't get it to stop. I ended up removing the battery. When the alarm goes off, it's very annoying. Since the other two were sticking to Zero (another brand), I tried to relax. We are in Arizona and the weather is mild (February 1st) so the heater didn't come on at all today or tonight, all appliances are electric. . The only other gas is the water heater in the garage. The device was in the living room when all the people were in the bedroom there was no one around it. Carbon monoxide monitoring is a big deal and I hope that the products designed for it will be thoroughly tested for reliability. Very disappointed with it. The return window for this was 30 days and the support/customer service window expired on 12/30/18 just 90 days after purchase. For such an important device and for $100 I expected it to last more than 4 months.