Document 8VXbBarmpxxonrqKVwnDgXL2o

1099 modernizes the concept of the NCRP standards of 1954, 1957 and 195S, obtain able as NCRP Rept No 39, PO Box 4867, Washington, D C 20008 Lasers The threshold limit values are for ex posure to laser radiation under conditions to which nearly all workers may be ex posed without adverse effects The values should be used as guides in the control of exposures and should not be regarded as fine lines between safe and dangerous levels They are based on the best avail able information from experimental studies Limiting apertures The TLVs expressed as radiant exposure or jrradiance in this section may be aver aged over an aperture of 1 mm except for TLVs for the eye m the spectral range of 400-1400 nm, which should be averaged over a 7 mm limiting aperture (pupil) No modification of the TLVs is permitted for pupil sizes less than 7 mm The TLVs for "extended sources" apply to sources which subtend an angle greater than r (Table 5) which varies with ex posure time This angle is not the beam divergence of the source Correction factor A (CFA) for eye ex posure All TLVs in Tables 3 and 4 are to be used as given for wavelengths 400 nm to 700 nm At all wavelengths greater than 1 06 fim and less than 14 fim the TLVs are to be increased by a factor of 5 TLV at wavelengths between 700 nm and 1 08 fim are to be increased by a uniformly extrapolated factor as shown in Figure 2 TABLE 3 THRESHOLD LIMIT VALUE FOR DIRECT OCULAR EXPOSURES (Intrabeam Viewing) from a Laser Beam Spectral Region Wave Length Exposure Time, (() Seconds TLV uvc UVB UVA Light 200 nm to 280 nm 280 nm to 302 nm 303 nm 304 nm 305 nm 306 nm 307 nm 308 nm 309 nm 310 nm 311 nm 312 nm 313 nm 314 nm 315 nm 315 nm to 400 nm 400 nm to 700 nm " *< Infrared A *' ** 44 700 nm to 1 08 Mm 1 06 pm to 1 40 am 700 nm to 1 06 Mm 1 06 pm to 1 4 pm Infrared B & C * 1 4 Mm to 103 Mm " 44 44 44 lO3 to 3 X 104 44 *' ** '* ** ** M M 10 to 10s 10s to 3 X 104 10- to 1 8 X 10-" 1 8 X 10-' to 10 10 to 104 104 to 3 X 104 10- to 10s 10- to 10* 10s to 3 X 104 10- to 107 10`7 to 10 10 to 3 x 104 3 mj cm-2 3 4 6 10 16 25 40 63 100 160 250 400 630 10 J " " cm'2 1 0 J cm-8 1 0 mW cm"2 5 x lO"7 J cm"2 T 18t 1 mj cm 10 mj cm"2 10 " W cm"2 [bght TLV's) X [CFA] (lightTLV) x 5 10"* [CFA] W cm'2 5 X lO 4 W cm 2 10-2J cm2 058 iTT J cm-2 01W cm*2 NOTE To aid in the determination of TLV's for exposure durations requiring calculations of fractional powers Figures 3, 4, and 6 may be used