NWCG Glossary of Wildland Fire (PMS 205)

Term	Steward	Status	Definition
virga	IWSC Incident Weather Subcommittee	Approved	Precipitation falling out of a cloud but evaporating before reaching the ground.
Virtual Instructor-led training (VILT)	QMC Qualifications Management Committee, TDSC Training Delivery Subcommittee	Approved	A type of ILT that is delivered as Distance Learning on an online platform, which is sometimes called a Virtual Classroom.
viscosity	ETSC Equipment/Technology Subcommittee	Approved	Thickness of a liquid, the degree to which it resists flow.
viscous water	ETSC Equipment/Technology Subcommittee	Approved	Water that contains a thickening agent to reduce surface runoff; tends to cling to burning fuels and spread in layers that are several times thicker than plain water, thereby having an increased capacity to absorb heat, cool fuel, and exclude oxygen.
visibility	FMSC Fuels Management Subcommittee, IWSC Incident Weather Subcommittee	Approved	The greatest horizontal distance at which selected objects can be seen and identified, or its equivalent derived from instrumental measurements.
visible area map	IOSC Incident Operations Subcommittee	Approved	Map showing the different classes of visible area covered by a lookout point or points; may differentiate between seen areas, indirectly visible areas, and blind areas, or only between seen areas and blind areas. Also known as seen area map.
Visual Flight Rules (VFR) conditions	AMC Aviation Management Committee	Approved	Basic weather conditions prescribed for flight under Visual Flight Rules: ceiling above 1,000 feet (300 m) and flight visibility in excess of 3 miles (5 km).
Visual Greenness (VG)	FDSC Fire Danger Subcommittee	Approved	An NDVI-derived image of vegetation greenness compared to a very green reference such as a golf course.
visual range	FMSC Fuels Management Subcommittee	Approved	Maximum distance at which a given object can just be seen by an observer with normal vision.
Visual Resource Management (VRM)	FMSC Fuels Management Subcommittee	Approved	The inventory and planning actions taken to identify visual values and to establish objectives for managing those values; and the management actions taken to achieve the visual management objectives.
visual resources	FMSC Fuels Management Subcommittee	Approved	The visible physical features on a landscape (e.g., land, water, vegetation, animals, structures and other features).
visual search	FISC Fire Investigation Subcommittee	Approved	A systematic and thorough scan of the wildland fire environment for an object or feature as it relates to seeing or sight.&nbsp; This scan may be aided by magnification when necessary.
volatile	PIC Public Information Management Committee, EPSC Education & Prevention Subcommittee	Approved	Readily changeable into vapor at low temperatures.
volatiles	IWSC Incident Weather Subcommittee	Approved	Readily vaporized organic materials which, when mixed with oxygen, are easily ignited.
volunteer	IOSC Incident Operations Subcommittee	Approved	An appointment/agreement that meets the following conditions: The person does not receive compensation (other than reasonable reimbursement or allowance for expenses actually incurred)
volunteer fire company	IOSC Incident Operations Subcommittee	Approved	A fire department company or a response unit, the members of which are not paid.
Volunteer Fire Department (VFD)	IOSC Incident Operations Subcommittee	Approved	A fire department of which some or all members are unpaid.
volunteer firefighter	IOSC Incident Operations Subcommittee	Approved	Legally enrolled firefighter under the fire department organization laws who devotes time and energy to community fire service without compensation other than Worker's Compensation or other similar death and injury benefits.
vortex turbulence	AMC Aviation Management Committee	Approved	Miniature whirlwinds trailing from the wingtips of any aircraft in flight. Vortex will be in the form of a horizontal whirlwind with velocities up to 25 mph (40 km) per hour or more. Also created by action of rotor blades on helicopters; these whirlwinds tend to move downward toward the ground. If an aircraft flies low over a fire, vortices may reach the ground and suddenly cause violent and erratic fire behavior.
walk test	SRC Safety/Risk Management Committee	Approved	The walk test is designed to determine the ability to carry out light duties. It consists of a one-mile test with no load that approximates an aerobic fitness score of 35. A time of 16 minutes, the passing score for this test, ensures the ability to meet emergency and evacuate to a safety zone.
warm front	IWSC Incident Weather Subcommittee	Approved	The leading edge of a relatively warm air mass which moves in such a way that warm air replaces colder air that moves away from a region. Winds associated with warm frontal activity are usually light and mixing is limited. The atmosphere is relatively stable when compared to cold front activity.
warp	MFES Mobile Fire Equipment Subcommittee	Approved	The amount of deviation from a straight line when the hose is hydrostatically tested; usually expressed in inches.
warrant	FBC Finance/Business Management Committee	Approved	The official delegation of authority to contracting officers and procurement officers establishing the dollar amount and type limits for acquisitions.
water bar	IOSC Incident Operations Subcommittee	Approved	A shallow channel or raised barrier, e.g., a ridge of packed earth or a thin pole laid diagonally across the surface of a road or trail so as to lead off water, particularly storm water. (Frequently installed in firelines on steep slopes to prevent erosion.)&nbsp;
Water Expansion Pumping System (WEPS)	ETSC Equipment/Technology Subcommittee	Approved	Apparatus utilizing an air compressor and positive displacement pump coupled to the same engine, plumbed to a non-pressurized tank, for producing foam. The operation involves injecting compressed air into a liquid stream containing a suitable foaming agent.

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