Bullard Glossary

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4-Point Suspension
A hard hat or cap suspension in which the weight of the hard hat shell is being distributed onto two crown straps that are connected to the shell in four locations.
6-Point Suspension
A hard hat or cap suspension in which the weight of the hard hat shell is being distributed onto three crown straps that are connected to the shell in six locations.
8-Point Suspension
A hard hat or cap suspension in which the weight of the hard hat shell is being distributed onto four crown straps that are connected to the shell in eight locations.
ABS
Acrylonitrile butadiene styrene. A rigid type of plastic.
Absolute Zero
Theoretical temperature at which all molecular activity stops or substances possess no thermal energy, equal to -273.15°C, or -459.67°F. Deep space is about 3° C above Absolute Zero.
Absorption
The ratio of how much infrared radiation is absorbed by a surface, and later emitted, as a percentage of the total amount of energy exposed to the surface. The percentage of absorption is basically equal to its emissivity.
Accuracy
A measure of the similarity of an instrument reading to the actual value for that reading. The accuracy of temperature measurement indicators on thermal imagers is affected by emissivity, the distance from the object, the angle of the object and a number of other factors.
Ambient Temperature
The temperature of the surrounding air and environment, which can impact the heat transfers around an object. Most temperature indicators on thermal imagers do not measure ambient air temperatures.
Amorphous Silicon
A material used to create infrared detectors. These types of detectors are used in a number of fire service thermal imagers.
Angstrom
A unit of measure equal to one-thousandth of a micron.
ANSI
American National Standards Institute
Aperture
A hole or opening that limits the amount of infrared radiation that reaches a detector. Bullard’s Thermal Throttle on the TIx and TI Commander is also called an aperture control.
APF / Assigned Protection Factor
The protection factor is the ratio of the contaminant concentration divided by the exposure limit (usually PEL or TLV). For example if the PEL is 100 ppm and the protection factor is 10, then the user will be protected against concentrations up to 1000 ppm.
APR
Air Purifying Respirator.
Aspect Ratio
The ratio of the horizontal width to the vertical length of a display. Many video displays are 4:3, as are the infrared detectors. This is the ratio of the common television. Some newer displays have a 16:9 aspect ratio.
Atmospheric Attenuation
The amount of signal reduction that occurs when infrared radiation travels through the atmosphere between the target and a thermal imager. Dust, humidity and precipitation can all reduce the effectiveness of the thermal imager, and the accuracy of any surface temperature measurement device.
Background Noise
The noise naturally present in an infrared detector, independent of the signal strength or ambient temperature. This is usually masked by software, but it may occasionally appear as image graininess in very bland scenes.
Binocular
A display device providing a separate display for each eye.
Blackbody
An ideal thermal radiator, normally used as a testing standard. The most common can be set to a specific temperature as the device emits almost 100% of the infrared radiation expected at a given temperature. Emissivity ratings are essentially a percentage value, compared to the blackbody. ( Emissivity = 1.0, Reflectance = 0.0, Transmittance = 0.0) An object that absorbs all electromagnetic radiation that falls onto it. No radiation passes through it and none is reflected
Bland Scene
A very stable scene viewed by a thermal imager. The scene is characterized by little temperature variation and a lack of strong emitters. Bland scenes can be difficult for thermal imagers to generate quality images.
Bolometer
A temperature measuring instrument using a strip thermistor to achieve higher sensitivity than a simple thermistor. Unlike thermistors which are used for contact temperature measurements, bolometers have been used to measure radiation levels.
Brow pad
The padded portion of the headband in a hard hat that sits on a user’s brow.
BST (Barium Strontium Titanate)
A material used to create infrared detectors. These types of detectors are used in a number of fire service thermal imagers.
Bucket Head
A material used to create infrared detectors. These types of detectors are used in a number of fire service thermal imagers.
Bump Cap
A hat or cap that is used where only protection from bumps and scrapes are a concern.
Calibration
The process of adjusting an instrument to read accurately under specific conditions.
Cap
A style of hard hat on which the brim is located only in the front.
CBRN
Chemical Biological Radiological Nuclear: This is the term often used for terrorist attack situations.
Celsius (Centigrade)
A scale for measuring temperature, where Absolute Zero is -273.2° C, water freezes at 0° C, and water boils at 100° C.
Chopper Wheel
A small wheel that rotates rapidly in front of a BST-based infrared detector. The wheel has a spiral cut out that partially blocks different portions of the detector momentarily. This process generates fluctuation in the amount of infrared energy reaching the detector, allowing it to create an accurate thermal image.
Conduction
The transfer of heat energy through a solid.
Convection
The transfer of heat energy through a liquid or gas due to the motion of that liquid or gas.
Crosshair
The intersecting vertical and horizontal line superimposed on the thermal imager display. It is commonly used to indicate the approximate area from which a thermal imager is taking a surface temperature reading. A small “+” shape that aids in aiming a thermal imager for temperature measurements.
Crown Straps
Ribbons in a hard hat or cap that distribute the weight of the shell onto a users head.
CSA
Canadian National Standards Institute
Degree
An increment of temperature measurement.
Detector (Infrared)
The individual chip or wafer that senses infrared energy.
Distance to Spot Ratio
A measurement of the area a pyrometer or radiometric thermal imager views from a specific distance. A 10:1 ratio indicates the surface temperature measurement taken at 10 feet is averaging an area of 1 square foot.
Electromagnetic Radiation
The field effects given off by accelerating a charged particle in a magnetic field. Depending on field strength and speed of acceleration, many types of electromagnetic radiation are created.
Electromagnetic Spectrum
A plot of the range of wavelengths and types of electromagnetic radiation found to exist from subsonic waves to cosmic rays. Radio waves, infrared energy and visible light are all portions of the spectrum.
Emissivity, Emission
The ability of an object to absorb and then radiate infrared energy. High emissivity ratings indicate good absorbers of infrared energy. Good reflectors of infrared are poor absorbers. The ratio of the radiation emitted by a surface to the radiation emited by a blackbody at the same temperature.
Engine
The core component of a thermal imager. This includes the FPA, the circuit boards that run the FPA, and the software that controls the FPA and interprets the signals to generate a thermal image.
F-number (f/#)
The ratio of focal length to aperture for a lens assembly. Smaller numbers represent faster lenses, which means that scene changes are conveyed to the detector more rapidly.
Fahrenheit
A temperature measurement scale, in which Absolute Zero is -459.7° F, water freezes at 32° F and water boils at 212° F.
Far Infrared
The longest wavelength of infrared radiation, measured as roughly 8 to 14 microns. This is the range used by fire service thermal imagers. Also referred to as Long Wave Infrared.
Ferroelectric
The physical property of a material that leads to thermal detection. This refers to the material’s ability to polarize as a direct result of temperature change. The stronger the relationship between temperature change and polarization, the better the material’s ability to function as a detector. The most common ferroelectric TI is BST-based.
Field of View (FOV)
The total field, measured as an angle, within which objects viewed by a thermal imager. Narrower FOVs generate more life-size images and distances, while wider FOVs place more image on the display. The most common FOV for fire service TIs is about 50°.
Flex-Gear®
Bullard patented flexible ratchet that flexes to the back of a users head.
FPA (Focal Plane Array)
The infrared detector itself, usually a thin wafer less than 1” square. The most common fire service FPAs are 320x240 pixels or 160x120 pixels.
Frequency
The number of cycles an operation occupies per period of time. The normal unit of measurement for frequency is Hertz (Hz), or cycles per second.
Full Brim
A style of hard hat on which the brim extends 360 degrees around the hat.
Hard Hat
A hat or cap that is designed to provide head protection.
Hat
A style of hard hat where the brim extends 360 degrees around the hat, also see full brim.
HDPE
High-density polyethylene, plastic used in most Bullard hard hats.
Headband
Part of the hard hat suspension that wraps around a users head to secure the hard hat to the head.
Heat
The energy or sensation that humans associate with infrared radiation.
Heat Sink
A device for dissipating heat; it absorbs heat by conduction from heat producing devices and dissipates heat by means of convection. Heat sinks are common inside older fire service thermal imagers to help maintain proper operating temperatures.
Heat Transfer
The flow of thermal energy from one object to another, by means of conduction, convection or radiation.
Hertz (Hz)
A unit for measuring frequency. One Hertz is one cycle per second.
Imager
A fully incorporated infrared detecting system that contains the detector, optics, processor, power source and display.
Infrared (IR)
electromagnetic radiation which occupies the band from 0.7 microns to 100 microns. infrared radiation is between the visible spectrum and microwave radiation.
Infrared-window
A protective cover, transparent to infrared radiation, placed on the front of a thermal imager to help protect the primary lens from damage. Many fire service thermal imagers use a germanium window.
Kelvin
The temperature scale used by scientists. The scale is based on the Celsius scale increments, but 0° is Absolute Zero rather than the freezing point of water.
LCD (Liquid Crystal Display)
A flat panel display system, common on many modern thermal imagers.
Lens
An optical component constructed of transparent substance with one or two curved surfaces of different curvature that has the ability to change the direction of beam travel. Infrared lenses are used for focusing the detector at a distance of interest and for modifying the size and distance of the focused field of interest.
Light
The region of the electromagnetic spectrum which is visible to the human eye. This is usually considered the region from 0.39 (violet) to 0.77 (red) microns.
Long Wave Infrared (LWIR)
The longest wavelength of infrared radiation, measured as roughly 8 to 14 microns. This is the range used by fire service thermal imagers. Also referred to as Far Infrared.
Microbolometer
A type of infrared detector that is capable of measuring absolute energy levels on each pixel of the FPA. Surface temperature measurement can be done directly from a microbolometer’s FPA.
Micron (micrometer)
A metric measurement equal to one-millionth of a meter.
Mid Infrared (or Mid-wave Infrared, MWIR)
Infrared radiation with wavelengths of roughly 3 to 8 microns.
Minimum Resolvable Temperature Difference (MRTD)
This number expresses the sensitivity of an infrared detector. It defines the smallest temperature difference the detector can differentiate. The lower the number, the more sensitive the unit is. Units with high levels of sensitivity (lower MRTD) tend to produce better, more defined images, especially in bland scenes.
Monocular
A viewing device made to produce an image for one eye only.
Near Infrared
The shortest wavelength infrared radiation, measuring approximately 1 to 3 microns. This is also referred to as Short Wave Infrared.
NETD (Noise Equivalent Temperature Difference)
This is a technical measure of sensitivity for a thermal imager, similar to the MRTD. Generally, a lower NETD will equate to more usable images, especially in bland scenes.
Operating Temperature Range
The acceptable temperature range for an infrared detector to remain calibrated and function properly. This refers to the temperature of the detector itself, not the ambient environment. The use of heat sinks, insulation and construction will affect how well a detector stays in its operating range, especially in a fire environment. Properly designed fire service thermal imagers will have other components that have a similar operating range as the detector.
PAPR
Powered Air-Purifying Respirator
PEL / Permissible Exposure Limit
This is the contaminant concentration that OSHA enforces. Subpart Z of 1910.1000 contains tables with contaminants and their PELs.
PEV
See Pyroelectric Vidicon.
Pressure Demand
A positive pressure atmosphere-supplying respirator that admits breathing air to the facepiece when the positive pressure is reduced inside the facepiece by inhalation. Reference: 29CFR1910.134(b)
Pinlock Suspensions
Suspensions on which sizing is adjusted by sliding the band and inserting pins into holes. (This is similar to baseball cap adjustments.)
Pixel (Picture element)
The smallest location size on a display or in memory. FPAs are measured in pixels, with each pixel generating a small portion of the thermal image.
PolarTec®
Trademarked material designed to keep skin dry when the wearer sweats. PolarTec features a patented bi-component knit construction that uses different yarns on either side of the fabric. This creates two different surfaces: one that is optimized to move moisture away from the skin, the other is designed to dry quickly.
PSI
Pounds per Square Inch: This is pressure.
Pyroelectric Vidicon
An outdated type of infrared detector. The sensor is based on hard or soft vacuum tube technology. These sensors tend to white out when exposed to strong infrared emitters and may become permanently damaged if exposed for a long period of time. Fire service thermal imagers are no longer manufactured with PEVs.
Pyrometer
An instrument used for non-contact measurement of surface temperatures. BST-based thermal imagers with temperature measurement have a pyrometer interlaced with the infrared detector.
Radiation
Heat transfer of energy in the form of electromagnetic waves. Forms of radiation include cosmic rays, gamma rays, x-rays, ultraviolet radiation, infrared, visible light, radio, audio and subsonic.
Radiometric
The ability of an infrared detector to measure, pixel by pixel, the actual scene temperature and display the results. Microbolometers can be radiometric.
Ratchet Suspensions
Suspensions on which sizing is adjusted by turning a knob on the headband.
Reflectance (Reflectivity)
The amount of total infrared radiation reflected by a surface. This value is frequently the inverse of the Absorption (Emissivity).
SAR
Supplied Air Respirator.
Saturation
The point at which an FPA or pixel cannot register any more infrared radiation. Saturated pixels will automatically be displayed as the hottest indicator (white, red, etc.) on the system. Also defined as the condition in which a further increase in infrared radiation produces no further increase in the displayed image.
SCBA
Self-Contained Breathing Apparatus: Bullard does not sell this type of respirator. Bullard does sell an ESCBA, which is a Pressure Demand Supplied Air Respirator with SCBA style egress bottle (Part No. SPECPDE).
Sensitivity
A measure of the minimum amplitude of input signal change to which an instrument will respond. On a thermal imager, this is a measurement of the smallest temperature differences the unit will detect.
Sensor
The component that converts radiation into electrical signals. This can refer to the detector itself, the engine or the entire thermal imager.
Short Wave Infrared (SWIR)
The shortest wavelength infrared radiation, measuring approximately 1 to 3 microns. This is also referred to as near infrared.
Shutter
A small device that repeatedly obstructs the FPA in a microbolometer thermal imager. The shutter covers the FPA, stopping all infrared energy from reaching the FPA. During the period the FPA is covered, the thermal imager verifies its calibrations. When this occurs, the image on the display will freeze momentarily. All microbolometers have a shutter.
Sportec®
Trademarked material designed to keep skin dry when the wearer sweats. Sportec features a patented bi-component knit construction that uses different yarns on either side of the fabric. This creates two different surfaces: one that is optimized to move moisture away from the skin, the other is designed to dry quickly.
SWIR
See Short Wave Infrared.
Temperature
An expression of thermal energy density, or how hot or cold an object is.
Temperature Range
The maximum to minimum temperature display capability of a system. This can be affected by the FPA, the engine’s software program or manufacturer’s selection.
Thermal Radiation
Electromagnetic energy whose natural wavelength fall between .7 and 100 microns, also called infrared radiation.
Thermistor
A device which measures temperature. The sensor for the thermistor is a semi-conducting resister whose resistance changes significantly with temperature.
Thermocouple
A device that measures temperature through conduction. The device reads temperature difference by measuring the difference in potential generated at the junction of two dissimilar metals.
Thermoelectric Cooling
A solid-state device that converts current into a temperature difference between two junctions. It is possible to put thermoelectric junctions in series or parallel to increase either the overall temperature drop or their power.
Thermography
The study of remote temperature measurement.
Thermoplastic
A general term used to describe a plastic that will hold up to high temperatures.
Three Ribs
Synonymous with Bullard head protection. Any hard hat sold in the US with three parallel ribs on top is made by Bullard.
TI (Thermal Imager)
A packaged, independently powered unit that detects infrared radiation and portrays that information on a video display for the user to interpret.
TIC (Thermal Imaging Camera)
See TI.
TLV / Threshold Limit Value
This is the contaminant concentration limit that American Conference of Government Industrial Hygienists (www.acgih.org) updates each year and is sometimes more stringent than the PEL.
Transmittance (Transmissivity)
A measurement of the ability of a material to pass radiation from one side to the other without absorbing or reflecting it. Infrared transmittance for most materials is near zero. Therefore, absorption/emissivity and reflectivity are usually inverse values.
Vanadium Oxide
A material used to create infrared detectors. These types of detectors are used in a number of fire service thermal imagers.
Wavelength
The distance between the two peaks of an energy wave cycle. Very long wavelengths may be measured in Hertz, or how frequently the peaks occur per second.
White Out
A condition that afflicted older infrared detectors. When the detector was exposed to strong infrared sources, such as fires, the thermal imager would generate completely white images on the display. Sometimes this was intentional in an effort to protect the detector from damage; sometimes it indicated damage to the detector. Modern thermal imagers do not white out; they may experience saturation.


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