Casella CEL CEL-281 - Manual (Page 114)

(Q=3 is normally used in ISO measurements of noise dose,
while Q=5 is specified for USA OSHA estimates of the risk of
hearing loss.)
8. Inspect the current criterion level by pressing the key once.
The criterion level is indicated on the main display, with Cri
shown in the lower-right corner.
9. Press the key slowly a sufficient number of times to obtain
the desired level.
(ISO normally requires a criterion level of 90 dB, while the USA
DOD standards use 84 dB, and OSHA 90 dB.)
The new criterion level is indicated on the main display.
10. Press the key again to see the result of dose calculation
using the new criterion level.
11. Inspect the current threshold level by pressing the key
once.
The threshold level is indicated on the main display, with Thr
shown in the lower-right corner.
12. Change the threshold level by slowly pressing the key a
sufficient number of times to obtain the desired level.
(USA OSHA standards use a threshold level of 80 dB.)
The new threshold level is indicated on the main display.
Obtaining Required Results
CEL-281 Operator's Handbook - Page 105