Though a lower setting will put the roller brush in closer contact with the carpet, carpet cleaning companies warn that it isn’t always desirable to do so. Some airflow is necessary in order to assist the suction action.
If the setting is too high, the vacuum action is rendered ineffective, as the pile blocks the entrance to the cleaner, and won’t pull the dirt into the machine.
Though some vacuum cleaners have as many as seven height settings, an increasing number of others are designed to adjust their height automatically without a loss of performance or convenience. Robotic cleaners also appear to adjust automatically to enable them to clean carpet, as well as hardwoods, tile and linoleum.
MORE: Clean Sweep: What's the Best Way to Vacuum?