The CMS (Center for Medicare & Medicare Services) requires that no patient items (cleaning basins, wash clothes, drinking cups, etc) be stored under a sink.
A state or community may have rules regulating what chemicals may be stored and how.
Common sense suggests that the following should not be stored under a sink:
(1) paper supplies
(2) harmful chemicals if the sink is accessible to a small child
(3) chemicals that are incompatible
(4) sterile supplies
(5) electrical equipment
There is no reason that certain cleaning or other supplies cannot be stored under a sink provided:
(1) the material is not listed above
(2) the healthcare facility has performed a risk assessment
(3) any chemicals are in appropriate containers and properly labeled
