To ensure a dry surface, the surface temperature must be how many degrees above the dew point temperature?

• A. 5 degrees below dew point
• B. 10 degrees above dew point
• C. Equal to the dew point
• D. 5 degrees above dew point

Answer: (D)

To keep a surface dry, you must keep it warmer than the dew point by a small margin. The dew point is the temperature at which air becomes saturated and water vapor starts to condense on surfaces. If the surface temperature drops to the dew point or below, condensation forms and the surface gets wet. To prevent that, you need the surface to run above the dew point.

A practical safety margin is five degrees above the dew point. This headroom accounts for small heat losses and temperature fluctuations, helping ensure the surface stays dry. Being five degrees below would promote condensation, being equal to the dew point would still produce dew, and while ten degrees above would certainly keep it dry, the standard requirement given is five degrees above.