The Occupational Safety and Health Administration (OSHA) has made it clear that eyewash stations should be checked at least twice per shift or use.
OSHA has also determined that eyewash stations should be checked for possible damage or other issues at least once a year. Another recommendation is that eyewash stations should be inspected during the first week of every month. If something major needs to be fixed, it is best to do it as soon as possible to minimize any hazards.