Question

Why is it a good idea to have a carbon monoxide detector in the home?

Answer 1

To avoid poisoning by a buildup of CO gas, choose 2!

Answer 2

It is a good idea because it helps to detect if there is too much carbon monoxide in the house. If there is too much, it can be poisonous and the detector will let you know. this answer would be TO AVOID POISONING BY A BUILDUP OF CO GAS. 
btw, is this platoweb? just curious.