1. The cleaning and maintenance personnel of the water tank must hold a sanitation certificate issued by the health department; unauthorized personnel are prohibited from entering the water tank.

2. Close the main inlet valve, shut off the valves connecting the tanks, open the drain valve, and empty the water from the tank.

3. Open the drain valve. Use a blower to blow over the tank opening for more than 30 minutes to allow air circulation, remove toxic gases from the tank, and blow in fresh air.

4. Light the candle and place it in the water tank to check if the air is oxygen, to confirm that there is sufficient air in the tank.

5. Clean and maintenance personnel to enter the tank for operation.