Scott Safety X190, Operating And Instruction Manual

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4.10 Emissivity And Its Effects On DDT
The accuracy of the relative temperature is affected by many factors, including the “emissivity” of the object. An object’s
emissivity is its ability to either absorb or reflect heat energy. The better the object’s characteristic to absorb heat (i.e. a high
emissive value), generally the more accurate the temperature reading.
The (DDT) installed in the X190 assumes an emissivity of 0.95. That is, for objects with emissivity of 0.95, the DDT returns
temperature readings accurate to within 10% of the actual temperature. The value of 0.95 was chosen because most
objects found in normal, traditional structural firefighting environments have an emissivity value close to 0.95. This gives the
firefighter the most accurate average temperature possible under these conditions.
When looking at shiny objects such as chrome, unpainted aluminum, unpainted stainless steel, and other metals, the DDT
temperature readings can be significantly distorted due to their emissivity. For painted objects, the emissivity of the paint,
rather than the emissivity of the actual material should be considered. When the temperature of metal objects are being
estimated using DDT, it is important to remember that painted metal objects generally return a much more accurate
temperature readout than unpainted metals.
Typical Emissivity Values
Material (Metals) Emissivity Material (Non-Metal) Emissivity
Aluminum Asbestos 0.95
Un-oxidized 0.02–0.1 Asphalt 0.95
Oxidized 0.2–0.4 Brick 0.90–0.98
Roughened 0.1–0.3 Ceramic 0.95
Brass Clay 0.95
Burnished 0.3 Concrete 0.95
Oxidized 0.5 Cloth 0.95
Copper Glass (plate) 0.85
Polished 0.03 Gravel 0.95
Roughened 0.05–0.1 Ice 0.98
Oxidized 0.4–0.8 Limestone 0.98
Iron Paint 0.90–0.99
Un-oxidized 0.05–0.2 Paper 0.95
Oxidized 0.5–0.95 Plastics (opaque) 0.95
Rusted 0.5–0.7 Rubber 0.95
Steel Sand 0.90
Cold-rolled 0.7–0.9 Snow 0.90
Ground sheet 0.4–0.6 Soil 0.90–0.98
Polished 0.1 Skin (human) 0.95–0.98
Oxidized 0.7–0.9 Water 0.93
Stainless 0.1–0.8 Wood (natural) 0.90–0.95
The cross-tabulation in the following table gives the user a general idea of the effective (real) temperature versus the
observed temperature, given varying emissivity levels. The higher the material’s emissivity value, the more accurate the
DDT reading.
Actual vs. Displayed Temperatures for Differing Emissivity
(Temperature of Surrounding = 70°F, and displayed temperature, degree F)
0 20 40 60 80 100 150 200 300 400 500 600 800 1000
0.1 104 231 423 563 793 996 1187 1373 1736 2093
0.2 -32 88 166 306 416 602 769 929 1084 1388 1688
0.3 -110 10 82 139 251 344 507 656 798 938 1211 1481
0.4 -155 -40 27 79 124 218 300 446 583 714 843 1096 1348
0.5 -172 -72 -11 36 77 114 196 269 403 530 653 774 1013 1250
0.6 -89 -37 6 43 76 108 179 246 371 490 606 721 949 1175
0.7 -53 -16 16 47 75 103 167 228 345 458 569 678 897 1114
0.8 -31 -3 24 50 75 99 157 214 324 431 537 643 853 1063
0.9 -16 7 30 52 74 96 149 202 306 409 511 613 816 1019
1 -5 15 34 54 74 93 143 192 291 389 488 587 784 981