A carbon monoxide alarm is a must with appliances that burn gas like propane stoves, furnaces and wood burning stoves. Carbon Monoxide (CO) is a is a colorless, odorless, and tasteless gas that is slightly less dense than air. It is toxic to humans when encountered in concentration. A CO alarm detects these deadly gases before they reach these problematic concentrations. We have used this Kidde brand for sometime and it works great! Its affordable (around $20) and is touted as the best selling detector on the market. It has a handy digital display and loud alarm to notify of toxic levels.