|| The deodorizing effect of weak acid hypochlorous solution against ammonia was investigated. When atomized particles of weak acid hypochlorous solution contacted ammonia, the ammonia concentration decreased in a concentration-dependent manner. The deodorizing effect was also observed against ammonia generated from the used floor cover for mice. When the floor mat was present, the ammonia concentration gently decreased but then rapidly decreased when the floor mat was removed. In the future, we will examine effective spraying conditions for weak acid hypochlorous solution in laboratory animal facilities, and we will also proceed with the validation of effects other than spraying.