Mo. Rev. Stat. § 196.475: Gas masks, alarm bell, and illumination required.

1. Any plant using a toxic gas refrigerant shall have at least one gas mask of a type approved by the department and shall keep the same where it will be readily accessible.

2. An alarm bell or buzzer provided with a suitable button shall be placed just inside the door of each locker room in a conspicuous place. Illumination shall be provided in the locker room at all times while open to the public, the switch operating same shall be accessible only to the operator.