Abstract: The Reconstruction program for the ventilation system in laboratory animal rooms was reported. The indoor inlet and outlet were installed with medium - efficacy filter and rough filter respectively. The fresh air was supplied by the original ventilation system. The indoor fresh air mixed with the circulating air was cooled or heated by the window air condition machines,and then pumped through tubular filter into the animal room. The reconstructed animal rooms reached the requirements of clean semi - barrier system with low cost and energy consuming.

Key words: Animal room, Reconstruction, “Tubular air filter””Semi-barrier system