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IAQ Glossary F


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F.P.M.: A measure of air velocity in feet per minute.

FACE VELOCITY: The velocity obtained by dividing the air quantity by the component face area.

FAN, CENTRIFUGAL: A fan rotor or wheel within a scroll type housing and including driving mechanism supports for either belt drive or direct connection.

FAN COIL UNIT (FCU): a small packaged unit for both heating and cooling one zone.

FAN PERFORMANCE CURVE: Fan performance curve refers to the constant speed performance curve. This is a graphical presentation of static or total pressure and power input over a range of air volume flow rate at a stated inlet density and fan speed. It may include static and mechanical efficiency curves. The range of air volume flow rate which is covered generally extends from shutoff (zero air volume flow rate) to free delivery (zero fan static pressure). The pressure curves are generally referred to as the pressure-volume curves.

FAN STATIC PRESSURE: The pressure added to the system by the fan. It equals the sum of pressure losses in the system minus the velocity pressure in the air at the fan inlet.

FAN, TUBEAXIAL: A propeller or disc type wheel within a cylinder and including driving mechanism supports for either belt drive or direct connection.

FAN, VANEAXIAL: A disc type wheel within a cylinder, a set of air guide vanes located either before or after the wheel and including driving mechanism supports for either belt drive or direct connection.

FEDERAL REGISTER: Publication of U.S. government documents officially promulgated under the law, documents whose validity depends upon such publication. It is published on each day following a government working day. It is, in effect, the daily supplement to the Code of Federal Regulations, CFR.

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FEVER: An abnormal temperature of the body above 98.6oF (37oC). Exercise, anxiety, and dehydration may increase the temperature of healthy people. Infection, nerve disease, cancer, anemia, and many drugs may cause fever. No single theory explains why the temperature is increased. Fever increases metabolism 7% per oC, meaning more food needs to be eaten. Convulsions may occur in children whose fevers tend to rise quickly. Confusion is seen with high fevers in adults and in children. It may begin quickly or gradually. The period of highest fever is called the stadium or fastigium. It may last for a few days or up to 3 weeks.

FILTER: A device to remove solid material from a fluid.

FILTER EFFICIENCY: The efficiency of various filters can be established on the basis of entrapped particles; i.e., collection efficiency, or on the basis of particles passed through the filter, i.e., penetration efficiency.

FILTER, HEPA: High-efficiency particulate air filter that is at least 99.97 percent efficient in removing thermally generated monodisperse dioctylphthalate smoke particles with a diameter of 0.3u.

FLOW COEFFICIENT: A correction factor used for figuring volume flow rate of a fluid through an orifice. This factor includes the effects of contraction and turbulence loss (covered by the coefficient of discharge), plus the compressibility effect, and the effect of an upstream velocity other than zero. Since the latter two effects are negligible in many instances, the flow Coefficient is often equal to the coefficient of discharge.

FLUID: Gas, vapor, or liquid.

FOLLOW UP TESTING: the testing designed to confirm the results of the initial testing using identical testing devices and similar test conditions.

FREE AREA: The actual measured perpendicular area between the fins of a grille or register.

FLYWHEEL EFFECT: In HVAC systems, to even out temperature variations in a building due to the temperature storage capabilities of the building's mass.

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FREQUENCY: The number of vibrations, waves, or cycles of any periodic phenomenon per second. In architectural acoustics, the interest lies in the audible frequency range of 20 to 20,000 cps Hertz (cycles per second).

FREQUENCY SPECTRUM: Usually a visual representation of a complex sound or noise which has been resolved into frequency components. The detailed nature of a complex sound may be studied by obtaining its frequency spectrum. Frequency spectra are commonly obtained in octave bands, 1/3-octave bands, and various narrow bands.

FRICTION: Friction is the resistance found at the duct and piping walls. Resistance creates a static pressure loss in systems. The primary purpose of a fan or pump is to produce a design volume of fluid at a pressure equal to the frictional resistance of the system and the other dynamic pressure losses of the components.

FUMES: Airborne solid particles usually less than 1 micrometer (um) in size formed by condensation of vapors, sublimation, distillation, calcination, or chemical reaction.

FUNGI: the unicellular of multi-cellular eukaryotic organisms embracing a large group of micro-flora including molds, mildews, yeasts, mushrooms, rusts, and smuts. Fungi are heterotrophic, i.e., requiring external food sources, as well as a source of nitrogen other than atmospheric nitrogen. Most fungi produce spores, which all broadcast through the air so that virtually all environmental surfaces will have some fungal material. Few fungi actually invade living cells and cause infectious disease. Most health effects are associated with allergic responses to antigenic material or toxic effects from mycotoxins. Another potential adverse indoor air effect of fungi is their ability to metabolize substrate material and generate certain volatile organic compounds.

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