What is "air gap"

Air gap \Air gap\ (Physics) An air-filled gap in a magnetic or electric circuit; specif., in a dynamo or motor, the space between the field-magnet poles and the armature; clearance.

An air gap, as it relates to the plumbing trade, is the unobstructed vertical space between the water outlet and the flood level of a fixture.

A simple example is the space between a wall mounted faucet and the sink rim (this space is the air gap). Water can easily flow from the faucet into the sink, but there is no way that water can flow from the sink into the faucet without modifying the system. This arrangement will prevent any contaminants in the sink from flowing into the potable water system by siphonage and is the least expensive form of backflow prevention.

A common use of the term "air gap" in home plumbing refers to a fixture that provides back-flow prevention for an installed dishwasher. This "air gap" is seen above the countertop as a small cylindrical fixture mounted parallel with the faucet. Below the countertop, the drain pipe of the dishwasher feeds the "top" of the air gap, and the "bottom" of the air gap is plumbed into the sink drain below the basket, or into a garbage disposal unit. When installed and maintained properly, the air gap works as described above, and prevents drain water from the sink from backing up into the dishwasher, possibly contaminating dishes. Water flowing from the fixture into the sink indicates a need for maintenance or repair.

To further illustrate the air gap, consider what could happen if the air gap were eliminated by attaching a hose to the faucet and lowering the hose into a sink full of contaminated water. Under the right conditions (if the water supply loses pressure and the sink is higher than the point at which the water supply enters the house, for instance), the dirty water in the sink will be siphoned into the water pipes through the hose and faucet. The dirty water then will be dispersed throughout the drinking water system.

An air gap, air wall or air gapping is a network security measure employed on one or more computers to ensure that a secure computer network is physically isolated from unsecured networks, such as the public Internet or an unsecured local area network. The name arises from the technique of creating a network that is physically separated (with a conceptual air gap) from all other networks. The air gap may not be completely literal, as networks employing the use of dedicated cryptographic devices that can tunnel packets over untrusted networks while avoiding packet rate or size variation can be considered air gapped, as there is no ability for computers on opposite sides of the gap to communicate.

Air gap may refer to:

• Air gap (magnetic core) used in inductors and some special transformers to allow more turns-current product (NI) without reaching core saturation
• Air gap (networking) in computer networks to isolate sections physically
• Air gap (plumbing) in context of plumbing
• Mid-Atlantic gap was the area not covered by American, British or Canadian air support during the Battle of the Atlantic in World War II
• Airgap (microelectronics) a microelectronics fabrication technique
• The space between magnetic pole pieces in which a voice coil operates