Aerodynamic diameter (AD); aerodynamic particle size The equivalent spherical diameter that approximates the aerodynamic behavior of an irregular-shaped particle.
Air-handling unit A component of a heating, ventilating, and air-conditioning (HVAC) system that delivers conditioned air and outside air to spaces in a building.
Arrestance test A filter efficiency test according to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 52.1 (ASHRAE, 1992) that utilizes an ASHRAE synthetic dust and the mass fraction of dust removed is determined.
Asymmetric warfare A military situation in which two belligerents of unequal strength interact and take advantage of their respective strengths and weaknesses.
Atmospheric dust-spot efficiency An evaluation used for high-efficiency filters, defined by ASHRAE Standard 52.1 (ASHRAE, 1992), that involves the use of unconditioned atmospheric air passed through the test material, and visualization of discoloration of the air downstream is compared to upstream (unfiltered) air.
Billeting Any building or portion of a building, regardless of population density, in which 11 or more unaccompanied personnel are routinely housed, including temporary lodging facilities and military family housing permanently converted to unaccompanied housing.
Bioaerosol A collection of airborne biological material including virus, bacterial cells, fungal spores, fragments, and by-products of microbial metabolism.
Building envelope The entire enclosing construction for a building, including walls, windows, doors and other openings, and roof.
Clinical sign (of disease) Objective evidence of disease especially as observed and interpreted by a physician rather than by the patient or a lay observer.
Collective protection A provision of a contaminant-free area in which personnel can function without individual protective equipment, such as a mask and protective garments.
Compartmentalization A division of interior spaces into separate, discrete spaces (see also “Zoning”).
Cost-benefit analysis A technique for project appraisal that weighs the total expected costs against the total expected benefits of one or more actions in order to choose the best or most profitable option.
Cyclone collection or separation A method that uses vortex flow to separate different sized particles.
Detect to treat Provide information in the time frame needed to initiate treatment options to minimize adverse health effects from exposure.
Detect to warn Provide information to initiate a response action that minimizes exposure.
Detection system A system that can recognize the presence of classes of threat agents but generally does not include identification. When unqualified, detection includes all the possibilities shown in Figure 3-1: clinical, symptomatic, visual, technology-based signatures, and assays. A detector technology system would refer to a technology-based detection system.
Detection technology Technology-based detection.
Detector A device that generally provides information on the presence of a threat agent or class of agent but does not reveal identity and is usually continuously operated. (See Figure 3-1 for types of detectors.)
Ducted return The use of an air-handling duct system to return air from the interior of a building to the air-handling unit.
Dust-holding capacity The amount of dust that an air cleaner can retain when it is operated at a specific airflow rate to a maximum resistance value.
Dust-spot filter A filter that is reported to remove 85 percent of particles 2.5 µm in diameter.
Electrostatic filtration The use of a charge field in a filtration unit to remove charged particles. Particles could be naturally charged or given a charge prior to filtration.
False alarm A wrong indication that a threat agent is present.
Filter bypass The airflow around the filter matrix caused by channeling of the filter material, overloading of the filter, use of incorrectly sized filters, or improper installation.
Filter efficiency The ability of a filter to remove particles from the air-stream.
Filtration A collection of particles larger than the filter pore size.
Heating, ventilating, and air-conditioning system A system designed to provide conditioned air to the various spaces in a building in order to satisfy demands for heating, cooling, humidification, dehumidification, and contaminant removal.
High-regret options Options to respond to a situation that could incur a high degree of remorse or serious consequences.
Identification system A system that determines the specific threat agent such that complete response actions, including medical treatment, are possible. (A caveat is that for unknown threat agents that have emerged or are engineered, identification can be delayed, such as for severe acute respiratory syndrome.) These can be exclusively technology based or human based or both.
Impactors A collection system in which particles are accelerated in a jet toward a surface (classical impactors) or toward a nozzle (virtual impactors).
Impingement filtration The retention of a particle when it is either too large or dense to follow the airstream around a fiber so that it lands on the surface and is retained due to attraction.
Infectious dose A number of pathogenic microorganisms needed to cause disease.
Infectivity The ability of pathogenic microorganisms to infect (that is, enter and multiply in) the cells of a host’s body.
Infiltration A flow of air from the exterior of a building to the interior.
Inhabited building A building or portion of a building routinely occupied by 11 or more personnel and with a population density of greater than one person per 40 gross square meters (430 gross square feet).
Leakage The flow of air through the building envelope—may be from the outside of a building to the interior or from the interior to the exterior.
Life-cycle cost All possible expenses incurred during the lifetime of a system. Life-cycle cost includes initial costs of implementation and all expenses incurred during the period of operation of equipment or a system.
Low-regret options Options to respond to a situation that could incur little remorse or not-so-serious consequences.
Metal oxide sensor A sensor that responds to virtually all organic vapors and provides information that a vapor release has occurred with little or no identification capability.
Minimum efficiency reporting value (MERV) A filter rating, defined by ASHRAE Standard 52.2 (ASHRAE, 1992), that is based on filtration efficiency as a function of particle size. Higher MERV values indicate more efficient filters.
Natural ventilation The use of open windows to supply outdoor air to interior spaces of a building.
Outside air intake A point of entry of outside air delivered to the spaces in a building by an air-handling unit.
Particulate Airborne solid material.
Pathogenicity The ability to cause disease.
Plenum return Unducted spaces, typically the cavity between the suspended ceiling and the floor or roof above, in which air from multiple areas in the building mixes before returning to the air-handling unit or being evacuated to the outside.
Polydispersed aerosols Aerosols whose particles are of various sizes.
Polymerase chain reaction (PCR) A molecular biology amplification method to detect and identify DNA sequences.
Prefilters Large porosity filters used to remove large particulate debris prior to the use of smaller porosity filters.
Remote sensing The ability to have a sensor at one location and to detect and identify the presence of a particular object at another.
Sensor network for distributed sensing The spatial distribution of sensors.
Sensor system A technology-based detection and identification system of threat agents that are localized at the collection point (for example, Biowatch is not a sensor system). Although sensor systems have the goal to identify the threat agent, this would be possible in many current applications only for limited sets of threat agents or would require off-site confirmatory identification.
Sensor technology A technology that provides information on the presence and possibly the identification of a threat agent or class of threat agents. Sensors and sensor technology may be operated intermittently or continuously.
Standoff The distance between a target (e.g., building) and a potential hostile event (e.g., explosion or chemical or biological agent release point).
Supply ductwork A positively pressurized conduit, typically made of sheet metal, used to distribute supply air to air delivered from the air-handling unit to spaces within a building.
TaqMan PCR A commercially available PCR method for detection of DNA and RNA.
Test bed An environment created for testing that contains the integral hardware, instrumentation, simulators, software tools, and other support elements to approximate a real-world situation.
Threat agent An agent used to inflict damage to a facility or harm to its occupants. Threat agents include biological, chemical, and radiological agents.
Threat type The combination of a threat agent and an implementation strategy used to inflict damage to a facility or to harm its occupants.
Tiered detection systems The staged deployment of typically inexpensive, fast-acting, low-accuracy detectors followed by more accurate sensors or confirmatory testing. Tiered detection systems are typically used to minimize the need for costly confirmatory tests. Tiered detection can also be spatially dispersed.
Transmissible The ability of pathogenic organisms to be transmitted from one person to another.
Trigger A detection technology that initiates an action and is generally more rapid, lower cost, and less specific than the identification technology.
Tropism An involuntary response of an organism or part of an organism toward or away from external stimuli.
Ultraviolet germicidal irradiation The use of various wavelengths of ultraviolet light (UVC, 200-280 nm and UVB, 280-315 nm) to inactivate biological materials.
Underfloor air distribution A system that utilizes underfloor space for distribution of air rather than overhead plenum space or supply ductwork.
Uninhabited buildings Spaces not considered inhabited, primary gathering, or billeting.
Zoning The process of defining areas served by independent HVAC systems.