A permit is not required for which type of mechanical work?

For mechanical work involving portable heating appliances, portable ventilation equipment, and portable cooling units, a permit is generally not required. This is because these types of equipment are considered temporary solutions that do not involve permanent installation or alteration of the existing mechanical systems in a building.

Portable heating appliances, for instance, can be moved and utilized without the need for extensive installation work. Similarly, portable ventilation and cooling units are designed for easy setup, typically needing only a power source and, in some cases, basic connection to existing ductwork, which does not justify the requirement for permits typically demanded for more permanent mechanical installations.

Overall, since all these items share the characteristic of being portable and not involving structural changes to a building's mechanical system, the conclusion is that a permit is not necessary for their use, aligning with building codes that aim to streamline compliance for temporary mechanical solutions.