Natural gas detectors monitor a home for the presence of methane, a natural gas that's used to run many home appliances. Methane levels can become too high if there's a gas leak.
Natural gas is colorless and odorless. Most gas companies add a chemical to natural gas that has a smell like rotten eggs. Without a natural gas detector, this smell is the only warning that a dangerous situation exists.
High levels of methane can lead to carbon monoxide poisoning. Carbon monoxide poisoning is more prevalent in the winter when there is less ventilation to the outside. Natural gas is also highly flammable. Under certain conditions, high levels of natural gas can cause an explosion.