Wis. Admin. Code § Cos 4.11 – Mobile Establishments.

In addition to the requirements of this chapter, a mobile establishment shall comply with the following requirements:

(1) Services shall not be provided unless a mobile establishment is parked, with the engine off, stable, and level.
(2) All services shall be provided inside the interior of the vehicle or structure.
(3) Carpeting is permitted only within driving or cab areas.
(4) All hazardous substances in a mobile establishment shall be stored upright in secured cabinets when the mobile establishment is moving. Regulations in s. Cos 3.01 (6) also apply to a mobile establishment.
(5) All moving parts, including slide outs and steps, shall be in good working order.