Question

For winter air conditioning, the relative humidity should not be more than __________%.

• A. 40
• B. 60
• C. 75
• D. 90

Hint:

Remember the comfort limits: Winter relative humidity is kept low (\(\le 40\%\)) to prevent condensation on cold walls, whereas Summer relative humidity can go up to \(60\%\).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Air conditioning involves the simultaneous control of temperature, relative humidity, air movement, and purity to maintain human comfort or optimum food storage conditions.
Different standards are specified for summer and winter air conditioning.

Step 2: Detailed Explanation:
For winter air conditioning, cold outdoor air is heated to maintain comfortable indoor temperatures (typically \(20\text{--}22^{\circ}\text{C}\)).
Heating cold air causes its relative humidity (RH) to drop significantly, creating dry indoor conditions that require humidification.
However, to maintain human physiological comfort and prevent structural problems:
1. The indoor relative humidity during winter should be maintained within a controlled range, typically \(30\%\) to \(40\%\).
2. The relative humidity should not exceed 40% in winter.
If the indoor relative humidity is higher than 40% during cold winter seasons, water vapor will rapidly condense as liquid water on cold interior surfaces (such as window panes, walls, and corners). This persistent condensation promotes the rapid growth of molds, mildews, and rot, deteriorating indoor air quality.
In contrast, summer air conditioning comfort allows for higher relative humidity limits (up to \(60\%\)).

Step 3: Final Answer:
Therefore, for winter air conditioning, relative humidity should not be more than 40%.