Smoke alarms sense smoke well before you can, alerting you to danger. In the event of fire, you may have as little as 2 minutes to escape safely, which is why smoke alarms need to be in every bedroom, outside of the sleeping areas (like a hallway), and on each level (including the basement). Do not put smoke alarms in your kitchen or bathrooms.
Carbon monoxide is an odorless, colorless gas that displaces oxygen in your body and brain and can render you unconscious before you even realize something is happening to you. Without vital oxygen, you are at risk of death from carbon monoxide poisoning in a short time. CO alarms detect the presence of carbon monoxide and alert you so you can get out, call 9-1-1, and let the professionals check your home.