1.   High over an air shaft, a caged canary sang.

2.   The police who entered Sunday carried gas masks and a caged canary that would alert them to any dangerous gasses.

3.   Many of the police wore protective clothing and gas masks and carried caged canaries to detect poison gas in the air.

4.   Investigators have carted off huge amounts of chemicals from Kamikuishiki over the last four days, using caged canaries as poison detectors.

5.   Investigators again took caged canaries to act as poison detectors as they entered the facility.

6.   A caged canary was prepared to detect toxic gas.