Cleaning staff MUST NOT bring to the site any chemicals they use at home, or that they might choose to use elsewhere.
Such chemicals may not be compatible with the chemicals held on site. (e.g., detergent from home may harm floor polish). They may be too aggressive and cause damage to surfaces.
They may also have poor labelling with insufficient warnings or first aid information, no Safety Data Sheet, and/or not provide enough information for an appropriate risk assessment.