The coolers covered by this specification are intended for use in areas where normal ambient, dry-bulb temperatures are 20°F (-6.67°C) or more in excess of the normal, wet-bulb temperatures. Successful cooling can be anticipated in areas with dry-bulb temperatures in excess of 85°F (29.44°C) and concurrent wet-bulb temperatures below 70°F (21.11°C). Moderate success can be expected with wet-bulb temperatures as high as 76°F (24.44°C). For general practice, use of the coolers when prevailing wet-bulb temperatures are above 72°F (22.22°C) is not recommended. The relationship between effective evaporative cooling and the spread between the dry-bulb and wet-bulb temperatures or the ambient air is as follows:

Wet-bulb depression Cooling effect (°F) (;C) 30 to 40 −1.11 to 4.44 Excellent 20 to 30 −6.67 to −1.11 Good 15 to 20 −9.44 to −6.67 Fair 10 to 15 −12.22 to −9.44 Marginal

Single cooler units are generally available with capacities ranging from 1,000 to 4,000 cfm (0.47 to 0.188 m³/s). For installations requiring greater capacities, multiple units may be required.