Final answer:
Relative humidity is the ratio of vapor density to saturation vapor density and is expressed as a percentage. For air at 25 ℃ with a vapor density of 9.40 g/m³, the relative humidity is approximately 40.9%, which is within the comfortable indoor range of 30 to 50 percent.
Step-by-step explanation:
The question deals with the concept of relative humidity, which is the ratio of vapor density to saturation vapor density, expressed as a percentage. To calculate the relative humidity in a specific example where the air temperature is 25 ℃ and contains 9.40 g/m³ of water vapor, we can use provided data to determine the dew point and the saturation vapor density. The dew point is identified when the relative humidity is 100%, which occurs at 10 ℃ for this vapor density. If the actual air temperature were 25 ℃, the saturation vapor density according to Table 13.5 would be 23.0 g/m³. Therefore, the percent relative humidity would be calculated using the formula:
percent relative humidity = (vapor density / saturation vapor density) x 100
Plugging in the values given:
percent relative humidity = (9.40 g/m³ / 23.0 g/m³) x 100 ≈ 40.9%
This calculated relative humidity is within the recommended comfort range of 40% to 60% indoors. To maintain a comfortable ambient room humidity, most vendors recommend keeping the indoor humidity between 30 and 50 percent. This can be monitored using a humidity gauge and adjusted with a humidifier or dehumidifier as necessary.