Dew point is the temperature at which air becomes 100% saturated with water vapour. Compressing air raises its dew point, so a dryer rated in pressure dew point (PDP) gives a much colder figure once that air expands to atmospheric pressure. Use this calculator to convert between pressure and atmospheric dew point, check the ISO 8573-1 water class and see which dryer type suits your target.
Pressure and atmospheric dew point
Pick a direction, then enter a dew point and your line pressure.
Atmospheric dew point
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ISO 8573-1:2010 water classes
| Class | Pressure dew point | Typical dryer |
|---|---|---|
| 1 | ≤ −70 °C | Heated or specialist desiccant |
| 2 | ≤ −40 °C | Desiccant (heatless or heated) |
| 3 | ≤ −20 °C | Desiccant or membrane |
| 4 | ≤ +3 °C | Refrigerated |
| 5 | ≤ +7 °C | Refrigerated |
| 6 | ≤ +10 °C | Refrigerated |