box-like structure enclosing a source of air contamination, with one open or partially open side into which air is moved for the purpose of containing and exhausting air contaminants and generally used for bench-scale laboratory operations, but not necessarily involving the use of bench or table.

1. delay in action of the sensing element of a control device due to the time required for the sensing element to reach equilibrium with the variable being controlled, i.e., temperature lag, flow lag, etc.

2. retardation of an output with respect to the causal input.

3. delay attributable to the transport of material or the finite rate of propagation of a signal or condition. Note: Also termed transport lag and transportation lag.

4. in thermal insulation, preformed narrow blocks attached around large pipes or vessels by wires or bands.

1. in gravity warm air heating, the duct running horizontally from the furnace to the riser, or stack. 

2. in plumbing, a water conductor from the roof to the storm drain.

in general, any operation designed to reveal a leak in a system.

1. nonreversible constant electric current component of the measured current that remains after the capacitive current and absorption current have disappeared. Note: Leakage current passes through the insulation volume, through any defects in the insulation, and across the insulation surface of solid or liquid insulation.

2. current that flows when a semiconductor device is in the off or blocked state (usually in the nanoampere range).

total leased line conductors between all interconnected data modems in a datatransmitting system.