An apparatus including a band; and a first device configured to attach to a person's wrist using the band; wherein the first device includes a first carbon monoxide level detector; wherein the first device includes a housing and a second device configured to be moved with respect to the housing from a first state to a second state; wherein in the first state a person cannot blow into the second device and cause a carbon monoxide level of the person's breath to be detected by the first carbon monoxide level detector; and wherein in the second state the person can blow into the second device and cause a carbon monoxide level of the person's breath to be detected by the first carbon monoxide level detector. The first device may include a second carbon monoxide level detector which is configured to detect a carbon monoxide level in ambient air.