What is the water content in the air, ppm?
At normal temperature and pressure, the water content in the air is usually between1,000 to 30,000 ppmBetween them, the specific value depends on temperature and relative humidity. The following is a systematic explanation of the influencing factors and quantitative relationships from a professional perspective:
1. Core influencing factors
- temperature effect
- For every 10 ° C increase in temperature, the water-holding capacity of the air approximately doubles. For example:
- At 0℃, the water content of saturated air is about 4.8 g/m³ (about 6,400 ppm);
- At 30 ° C, the water content of saturated air rises to 30.4 g/m³ (approximately 40,500 ppm).
- For every 10 ° C increase in temperature, the water-holding capacity of the air approximately doubles. For example:
- Relative humidity (RH) control
- For every 20% decrease in relative humidity, the water content decreases by about 40%. For example:
- At RH=80%, the water content is about 18,400 ppm;
- At RH=50%, the water content drops to 11,500 ppm.
- For every 20% decrease in relative humidity, the water content decreases by about 40%. For example:
2. Quantitative data for typical scenarios
| environmental conditions | Water content range (ppm) | typical application scenarios |
|---|---|---|
| Dry environment (RH<30%) | 3,000~8,000 | Electronics manufacturing workshop, archives room |
| Ordinary indoor (RH=50%) | 11,500~13,800 | Offices, laboratories |
| Humid environment (RH=80%) | 18,400~23,000 | Greenhouse, bathroom |
| Saturated air (RH=100%) | 23,000~40,500 | Air and compressed air system inlet after rain (untreated) |
3. Control standards in industrial applications
- compressed air system
- Pharmaceutical/food industry: Require water content <500ppm (dew point <-20℃);
- General Industry: Water content <1,000 ppm (dew point <0℃) can meet the needs of most pneumatic tools.
- special technological requirements
- Semiconductor manufacturing: It is necessary to control the water content of <10ppm (dew point <-70℃), which is achieved through an adsorption dryer;
- Spraying process: Water content <500ppm can avoid coating bubble defects.
4. Detection and control technology
- on-line monitoring
- Capacitive or alumina sensors are used to measure water content in real time with an accuracy of ±50ppm.
- Drying equipment selection
- Freeze dryer: can process dew point of 3~10℃ (water content 1,150~ 8,000 ppm);
- Adsorption dryer: It can achieve a dew point of-40~-70℃ (water content <50ppm).
conclusion
The water content in the air is significantly affected by temperature and humidity conditions, and is usually between 1,000 and 30,000 ppm at normal temperature and pressure. In industrial applications, it is necessary to select appropriate drying technology according to process requirements, and ensure the quality of compressed air through online monitoring. For example, the pharmaceutical industry needs to control the water content below 500ppm, while precision electronics manufacturing needs to further reduce it to 10ppm to ensure product quality and production safety.