ABS Plastics
Acrylonitrile-butadiene-styrene plastics are used extensively in the molding of vacuum cleaner cases and trim parts. It is an economical plastic which is lightweight but strong and resists stains and chemicals. See also our article on External Structure Materials & Durability

Activated Charcoal
Charcoal from which most of the impurities have been removed. It is made by treating ordinary charcoal with steam and air heated to above 600 degrees Fahrenheit. It is the best adsorbent since its many empty spaces give it a large internal surface to hold particles.

Agitation
The process of moving in a rapid and violent manner. Carpet is usually agitated by the brushes and sometimes a beater bar on the revolving brush roll in a vacuum cleaner. See also our article on the Effects of Brushing Action.

Air Flow
The movement of air from one location to another. In a vacuum cleaner, it generally refers to the movement of air through the vacuum cleaner or central vacuum system and is measured in cubic feet per minute (C.F.M.). It is one of the most important aspects of vacuum cleaner performance. Air flow in a vacuum cleaner is inversely proportional to the total resistance within the system and directly proportional to the suction created by the suction motor. For additional information, see our article on Air Flow through the System.

Air Pressure
The pressure of atmospheric or compressed air. At sea level, atmospheric pressure is 1,013.2 millibars or 14.69 pounds per square inch. A vacuum cleaner's suction motor reduces the air pressure in order to create air flow. See also our article on Fan or Impeller Types & Performance.

Air Watts
A specification developed in an effort to rate the output power of the vacuum cleaner instead of its input power. It is based on suction with air flow as measured at the vacuum cleaner inlet. See also our article on the Power of the Suction Motor.

Allergen Filtration Bags
A special name Hoover gives to their high filtration bags. They are also known as MicroFiltration dustbags. According to Hoover, this dustbag "Traps 99% of particles down to 5 microns! Filters a wide range of airborne particles including many pollens, spores, other allergens and dust mites. Ideal for many with dust related or allergic discomforts. Electrostatically charged liner enhances the capture of extremely fine particles." For more information, see Bag Performance and Filtration Efficiency.

Amperage (Amps)
The strength of an electric current flowing through a wire or other electrical conductor expressed in amperes (amps). One ampere of current will flow through a conductor having one ohm of resistance when a potential of one volt is applied to it. Vacuum cleaners are often rated by the amount of amperage drawn from the electrical outlet which flows through them. The maximum permitted for UL Approval is 12 Amps. See also our articles on the Power of the Suction Motor and Efficiency and Performance Ratings.

Armature
An armature is made of a laminated steel core which is wound with copper enamel-insulated wire. The windings are attached to a copper commutator near one end of the armature. It can be considered the heart of a motor since it is the armature's rotation, motivated by electrically created magnetic fields within the motor, that converts electrical energy into mechanical energy. See also our article on the Suction Motor Design & Operation.

Bakelite
Bakelite is an important thermosetting resin made from phenol and formaldehyde which can be injection molded to make parts which are resistant to heat, chemicals and moisture. See also our article on External Structure Materials & Durability.

Ball Bearing
A low friction type of bearing in which round steel balls rotate between a spinning inner race (small steel ring with a rounded grove on it's outer surface) and a stationary outer race (larger steel ring with a rounded grove on it's inner surface). The sides often have shield or seal rings to retain the grease and keep the bearing as clean as possible.

Beater Bar
A long rigid bar or raised area on a revolving brush roll which pushes the carpet away from the roll, creating a rapid beating action. Stiff bristles on a brush roll can have a similar effect.

Beating Action
The rapid hitting action caused by a beater bar or stiff bristles on a brush roll. The effect of this is to help work the dirt and grit toward the top of the carpet.

Brush Roll
The brush roll is the part of a vacuum cleaner which contains rows of bristles and sometimes beater bars to agitate the carpet in order to significantly aid in the removal of dirt from it. While often being in the shape of a cylinder, some are contoured, being more like an auger in appearance. It is mounted in the nozzle by its ends and contains bearings which allow it to be rotated at a high speed by the brush motor or turbine. Most vacuum cleaners use the same motor to create the suction and rotate the brush roll.

Brushing Action
The act of brushing a carpet's fibers, often by a revolving brush roll. This is a significant part of the agitation process performed by an upright or power nozzle, effectively removing dirt from the carpets.

Bypass Cooling
A type of motor cooling design which incorporates a separate air flow through the motor to cool it. The main air flow, which picks up the dirt, travels through the suction fan or fans but bypasses the motor itself. This prevents residual dirt or moisture in the main air flow from coming in contact with the armature, field, carbon brushes, etc. Bypass cooling is always incorporated in wet/dry vacuum cleaners as well as the traditional "dirty air" uprights. A motor is either a bypass cooled type or a flow through (FlowThru) cooled type.

C.F.M.
Represents Cubic Feet per Minute. The specification typically used to indicate the amount of air flow which will pass through a clean vacuum cleaner power unit when running by itself. When rating the main power unit of a central vacuum system, it is normally measured at the 2" opening where the 2" piping will be attached. See also Air Flow.

Canister Type
The type of vacuum cleaner that houses the suction motor and filtering system in a somewhat square or rectangular container. Typically incorporating a "clean-air" system, they are known for producing strong suction for use with the attachments. When a power nozzle is part of the system it is often referred to as a "power team." A canister type vacuum cleaner usually contains wheels which allow it to be pulled after the user by its hose. See also our article on the Standard Canister type.

Central Vacuum System
A stationary type of canister vacuum cleaner which is usually mounted in the basement or garage. Being stationary, the units usually have larger and more powerful motors than those that can be used in the portable vacuum cleaners. Hose inlets are mounted in the walls and 2" PVC pipe is installed to carry the dirt laden air to the central power unit. A special 30' long hose allows the user to conveniently reach into every part of the house to effectively clean it. Performance in central systems is greatly enhances by the use of a power nozzle containing a motor driven revolving brush roll to deep clean carpets. These systems are often highly recommended by allergists since the main air flow is typically exhausted outside the house, preventing the recirculation of fine dust and allergens within the house. For examples of excellent systems, see our list of Ristenbatt Vacuum's Preferred Models. See also our article on the Central Vacuum System.

Clean-Air Design
A vacuum cleaner design in which the air flow which picks up the dirt is cleaned by the filtering system before it passes through the fan or fans of the suction motor. This design eliminates fan breakage problems which can be caused when objects are picked up by a dirty-air system. Also, it typically produces significantly more suction, especially when a hose and attachments are used. See also our articles on Fan or Impeller Types & Performance and the "Clean-Air" Upright type of vacuum cleaner.

Cleaning Effectiveness
There are two different ways of viewing cleaning effectiveness. The most common use has to do with the ability of a vacuum cleaner to pick up dirt from the surface being cleaned. The other has to do with the ability of the filtering system to clean the air so a minimum amount of dirt and allergens is recirculated back into the home.

Cleaning Performance Rating
Hoover defines their Cleaning Perfomance Rating as follows: "This Hoover Cleaning Performance System is for comparing the Relative Progressive Performance of Hoover uprights only and not for comparison with any other brands. The majority of this rating is based upon the American Society for Testing and Materials (ASTM) carpet cleaning effectiveness testing (ASTM Test F608). Other performace factors include hose power (ASTM Test F558), surface litter cleaning, hard floor cleaning, edge cleaning, cleaning width and air filtration." For additional information on Hoover ratings, see our article on Hoover's Efficiency and Performance Ratings.

Commutator
A commutator is the part of an armature which has individual bars of copper which are positioned in the shape of a drum. The motor brushes are held against the commutator in order to carry the electrical current to the armature windings which are connected to it.

Current
Electrically speaking, the flow of electrical charges through a wire or conductor. Usually rated as amperage (amps).

Cyclonic
Relative to filtration systems, cyclonic systems separate the dust particles from the air flow by spinning the air within a separation chamber. The spinning causes centrifugal force to act upon the dust particles, moving them outward while the air exits from the inner part of the chamber. Some cleaners use multiple chambers and most cleaners add filters to increase the total system filtration efficiency.

Direct Air System
A vacuum cleaner design in which the air flow which picked up the dirt passes directly through the fan of the suction motor and into the bag. While usually not producing as much suction for use with attachments, this design often will produce more air flow when working with large openings and short air flow distances. This is another name for a system using the Dirty-Air or traditional upright design.

Dirty-Air Design
A vacuum cleaner design in which the air flow which picked up the dirt passes through the fan of the suction motor before it is cleaned by the filtering system. An upright with this design can also be said to use the Traditional Upright Design since most uprights used this design since their inception. While usually not producing as much suction for use with attachments, this design often will produce more air flow when working with large openings and short air flow distances. Therefore, this design in an upright usually performs well when cleaning carpets. See also our articles on Fan or Impeller Types & Performance and the Traditional Upright type of vacuum cleaner.

Edge Brushing
On many newer power nozzles and uprights, the brush roll is designed so that its bristles reach fairly close to the edges of the nozzle to enable brushing very close to the carpet's edges. Dual edge brushing (both sides) can be obtained by running the belt either in the center of the roll or a few inches from one end instead of at the very end of the roll.

Efficiency Rating
There are two completely different ways to rate the efficiency of a vacuum cleaner. The most important way of stating the efficiency has to do with rating how well a vacuum cleaner filters the air to remove dust and allergens. The HEPA and ULPA specifications use this type of rating. The other way of viewing the efficiency rating has to do with stating the cleaning effectiveness relative to the amount of power being used to produce it. A great deal of confusion existed a few years ago as a result of an efficiency rating which The Hoover Company used as described in our article on Hoover's Efficiency and Performance Ratings.