Due to many Japanese houses are built in wood, fire is very important concern to prevent. Especially during the winter, the humidity is very low, the air will become extremely dry, which makes the fire to burn more quickly.
Major causes of fire are smoking on bed, cooking and the stove. Fire caused by cooking is mostly happens when someone is cooking tempura, which uses a plenty of oil due to no one uses electric deep fryer for cooking tempura. Actually almost no one uses deep fryer at all.
Therefore putting fire detectors and placing fire extinguishers are the strict orders by the fire brigades in Japan, which prevention of fire is one of their main activities. City of Edo(current Tokyo. The most populated city on Earth) suffered by big fires which broke out several times during Edo period; 17th and 18th centuries. Due to no fire engines and even no fire hydrants, the fire fighters had to break down the burning houses immediately to prevent the fire to spread. Also the resident who made the fire was punished nevertheless it was caused by accident.
Although there are modern fire brigades in Japan, please kindly do not smoke on bed and please use portable ashtray when smoking outside.