HVAC. Relative Humidity

Question 0

Absolute humidity is

Answer 0

the mass of water vapor divided by the mass of dry air in a volume of air at a given temperature. The hotter the air is, the more water it can contain.

Question 1

Humidity can be measured in several ways, but ____________ is the most common.

Answer 1

Relative Humidity.

In order to understand relative humidity, it is helpful to first understand absolute humidity.

Question 2

Relative humidity is the ratio of

Answer 2

the current absolute humidity to the highest possible absolute humidity (which depends on the current air temperature).

Question 3

A reading of 100 percent relative humidity means that

Answer 3

the air is totally saturated with water vapor and cannot hold any more, creatin­g the possibility of rain. This doesn’t mean that the relative humidity must be 100 percent in order for it to rain – it must be 100 percent where the clouds are forming, but the relative humidity near the ground could be much less.

Question 4

Humans are very sensitive to humidity, as the skin relies on the air to get rid of moisture. The process of sweating is

Answer 4

your body’s attempt to keep cool and maintain its current temperature.

Question 5

If the air is at 100-percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high.

Answer 5

If the relative humidity is low, we can feel much cooler than the actual temperature because our sweat evaporates easily, cooling ­us off.

Question 6

People tend to feel most comfortable at a relative humidity of about

Answer 6

45 percent. Humidifiers and dehumidifiers help to keep indoor humidity at a comfortable level.