Ill. Admin. Code tit. 35, § 604.1115
c) Chlorine gas feed and storage must be enclosed and separated from other operating areas. Both the feed and storage rooms must be constructed so as to meet the following requirements:
7) air intake and exhaust louvers must facilitate airtight closure;
A) Outside switches must be protected from vandalism.
1) vacuum regulators on all individual cylinders in service;
3) restrained in position;