For the purpose of this article, certain terms and words shall be interpreted and defined as follows:
(a) "Decibel" means a unit of measurement of the intensity of loudness of sound. Sound level meters are used to measure such intensities and are calibrated in decibels.
(b) "Flash point" means the lowest temperature at which a combustible liquid under prescribed conditions will give off a flammable vapor which will burn momentarily using the closed cup method.
(c) "Foot-candle" means a unit of illumination equivalent to the illumination at all points which are one foot distant from a uniform source of one candlepower.
(d) "Free burning" means a rate of combustion described by a material which burns actively and easily supports combustion.
(e) "Intense burning" means a rate of combustion described by a material that burns with a high degree of activity and is consumed rapidly.
(f) "Moderate burning" means a rate of combustion described by a material which supports combustion and is consumed slowly as it burns.
(g) "Octave band" means all of the frequencies from one given frequency to a second. In sound octave bands, the second frequency is usually twice the first one.
(h) "Octave band filter" means an electrical device which separates the sounds in each octave band and presents them to the sound level meter.
(i) "Particulate matter" means finely divided liquid or solid material which is discharged and carried along in the air.
(j) "Residence district" means a district designated primarily for residential use in this Zoning Ordinance.
(k) "Resultant displacement" means the maximum amount of motion in any direction and shall be determined by means of any three component (simultaneous) measuring system approved by the Planning Commission.
(1) "Ringelmann number" means the number of the area on the Ringelmann chart that most nearly matches the light-obscuring capacity of smoke. The Ringelmann chart is described in the U. S. Bureau of Mines Information Circular 6888, on which are illustrated graduated shades of gray for use in estimating smoke density. Smoke below the density of Ringelmann No. 1 shall be considered no smoke or Ringelmann No. 0.
(m) "Slow burning or incombustible" means materials which do not in themselves constitute an active fuel for the spread of combustion, or a material which will not ignite, nor actively support combustion during an exposure for five (5) minutes to a temperature of 1200°F.
(n) "Smoke" means small gas borne particles resulting from incomplete combustion, consisting predominantly of carbon and other incombustible material, excluding metallurgical fume and dust, and present in sufficient quantity to be observable independently of the presence of other solids.
(o) "Smoke unit" means the number obtained when the smoke density in Ringelmann number is multiplied by the time of emission in minutes. For the purpose of this calculation, a Ringelmann density reading shall be made at least once a minute during the period of observation; each reading is then multiplied by the time in minutes during which it is observed. The various products are then added together to give the total number of smoke units observed during the entire observation period.
(p) "Three component measuring system" means instrumentation which can measure earth borne vibrations in three directions, that is, vibration occurring in a horizontal as well as a vertical plane.
(q) "Vibration" means oscillatory motion transmitted through the ground.
(1969 Code §27-31)