Dell OptiPlex 3020–Mini Tower Owner's Manual page 58

Feature
Altitude:
Operating
Storage
Airborne contaminant level
58
Specification
–15.2 m to 3048 m (–50 to 10,000 ft)
–15.20 m to 10,668 m (–50 ft to 35,000 ft)
G1 or lower as defined by ANSI/ISA-S71.04-1985