Plumbing: A permit is not required when a plumber is called out for an emergency. This can include repairs and stopping of leaks in drains, water, soil, waste or vent pipes not concealed by walls or ceilings. Also, the clearing of stoppages or the repairing of leaks in pipes, valves or fixtures, and the removal and re-installation of water closets (toilets), provided the repair do not involve or require the replacement or rearrangement of valves, pipes or fixtures.
Electrical: A permit is not required for minor repair work, including the replacement of lamps or the connection of approved portable electrical equipment to approved permanently installed receptacles.
Gas: A permit is not required for gas-fueled portable heating, cooking or clothes-drying appliances.
Heating and Cooling: A permit is not required for installation of portable heating, ventilation and cooling appliances that connect to permanently install electrical receptacles.
A mechanical permit application can be found at Mechanical Permit Application