Instruct: Classify the given Amazon review as either positive or negative.
Query: Had a serious gas leak: no alarm

I could live with the few false alarms we had with our unit - but in January, when a knob on our natural gas stove had been left partially "on" - I came home to a house sickeningly filled with gas - and the Nighthawk blithely read "0 PPM". No alarm - not a peep. It was by the Grace of God that my house didn't explode when I flipped on the light switch before I smelled the gas. An hour after opening all the doors and windows, our utility technician arrived - and her "gas sniffer" went crazy - it was still reading 4% concentration of gas. I'm sure the initial concentration had been 3+ times that much.If my light switch had sparked - I could have been killed. For this unit to NOT have sounded any kind of alarm is truly scary.