Important Central Vacuum Definitions
Demand to be treated like an intelligent person. Don't get sucked in!
The majority of vacuum cleaner distributors do not provide or explain meaningful specifications because it makes it possible to make informed comparisons with their competitors' products. Providing poorly understood or irrelevant specifications is a marketing technique which is used to blatantly manipulate the unsophisticated buyer. The vast majority of retail sales people don't know better either.
The higher the Air Watts... The better the pick up!
Air watts is a combination of water lift (suction) and CFM (airflow). This is the truest measure of cleaning power.
Air Watts is recognized by the American Society of Testing and Materials (ASTM) as the best way to measure the actual cleaning power of a vacuum system. 99% of all central vacuum manufactures measure the power of their units by Air watts. This is calculated using the formula:
(Air Flow (in CFM) x Vacuum (in inches of water lift))/8.5 = Air Watts.
Suction (also called Vacuum or Waterlift)
A vacuum's ability to lift is a valid measurement. In fact, it is called vacuum, or water lift. This suction power creates the lift and velocity of air which sweeps dirt away. The suction capacity of a vacuum is not the key to effective vacuuming. The real key is how much air the vacuum moves and how fast it moves it.
Airflow or CFM (Cubic Feet Per Minute)
CFM (air flow) is crucial for vacuum cleaning. This measures the "volume" of air the motor is capable of moving. Debris can only be pulled into a vacuum if there is sufficient air being circulated. Filtration, piping, hoses and accessories all restrict and reduce the amount of actual Airflow a system has.
Noise Level: (Decibals - dBA)
The other factor that should be considered is noise level. Many vacuum cleaners are notoriously noisy. This is not the place to discuss the many unpleasant effects that high noise levels can have on people's health and general well being. Suffice it to say that you should be prepared to pay a premium for a really quiet vacuum cleaner.
Noise levels are measured in decibels. Decibel levels in excess of, let's say 70dBA or so, are not only unpleasant; they can hurt you, and they are unnecessary.