Final answer:
A household fire alarm should be replaced every 10 years, as recommended by the National Fire Protection Association (NFPA). Carbon monoxide alarms have a lifespan of around 7-10 years.
Step-by-step explanation:
The lifespan of a household fire alarm depends on various factors, including the type of alarm and its maintenance. Generally, a smoke alarm should be replaced every 10 years, as recommended by the National Fire Protection Association (NFPA). Carbon monoxide alarms also have a lifespan of around 7-10 years. It is important to regularly test and replace batteries, as well as follow the manufacturer's instructions and recommendations.