Why did Montag want Faber to turn on the air conditioning and sprinklers?

This is so the mechanical hounds will loose his scent. 

Montag has stepped on the grass and been inside Faber's house. The Mechanical Hound can track Montag to Faber's, putting him in danger. Montag does not want to endanger Faber because of him and needs their plan to be accompolished. The air conditioner and sprinkeler will hide his scent.