According to the purpose of humidification, they can be broadly categorized into two types:

1. Comfortable humidification

According to statistical analyses in the international HVAC community, humans feel most comfortable and achieve the highest work efficiency when living and working in environments with temperatures ranging from 22 to 26°C and relative humidity levels between 40% and 65% RH. Dry air, on the other hand, can lead to:

The airborne dust levels have significantly increased, causing dryness and itching of the skin, making people feel uncomfortable. Typically, such an environment serves as a breeding ground for various bacteria, leading to colds and sore throats, greatly increasing the likelihood of bronchitis and skin diseases, thereby driving up sick leave rates and indirectly affecting productivity.

2. Process-oriented humidification

(1) Electronics factories, optoelectronics factories, and semiconductor factories

Humidification can prevent static electricity caused by excessively low relative humidity in the air. This static electricity may lead to equipment malfunctions and an increase in product defect rates.

Electronics factories, optoelectronic facilities, and semiconductor plants generally maintain a constant temperature of around 22°C. Therefore, year-round air conditioning and precise control of temperature and humidity are essential to prevent static electricity, condensation and dew formation, corrosion, fiber breakage, and discomfort among workers. Since relative humidity above 60% can lead to corrosion, while relative humidity below 40% can cause static electricity, components typically need to be kept in a specific temperature and humidity environment before entering the cleanroom. This prevents condensation and dew formation due to temperature differences upon entry into the cleanroom, which could otherwise cause moisture damage to the components; or generate static electricity that easily attracts dust and impurities, compromising component quality and functionality.

(2) Hospitals, operating rooms, intensive care units, and nursing care facilities

Proper humidity control not only helps reduce odors but also enhances patients’ physical and psychological comfort and accelerates wound healing. Typically, governments or relevant authorities have established regulations or restrictions on air-conditioning environments in different areas of hospitals; please refer to the table below for details:

These venues typically employ steam humidification, as steam is a high-temperature sterilized gas that is free of bacteria. However, it’s important to ensure that the humidification system does not exhibit any dripping or condensation, as these could create breeding grounds for pathogens. For an optimal humidification system, in addition to recommending steam humidification, it’s also advisable to use fast-absorbing diffusers and equip the system with a highly efficient proportional control system to ensure perfect compatibility.

(3) Textile mills, paper mills, and printing plants

Air humidification can prevent fiber cracking and static electricity caused by excessively low relative humidity in the air, thereby avoiding disruptions in the production process and ensuring high product quality. The recommended temperature and humidity levels are as follows:

(4) Tobacco factories, painting plants, detonator manufacturing facilities, precision machining workshops, cold storage and fresh-keeping warehouses, bowling alleys, computer rooms, and programmable control rooms.

(5) Inspection or Environmental Testing Organizations: Widely used for the inspection of consumer products, they fall into two main categories.

1. Weathering tests: These include individual tests for temperature, humidity, corrosion, or fungal growth; or tests involving various combinations of the aforementioned factors.

2. Dynamic testing: Includes vibration, electric shock, acceleration, radiation, or pressure testing.

General-purpose laboratories typically have a wide temperature range (2~ 85℃ ) and relative humidity (2–98% RH) to meet the requirements of different testing environments.

(6) Libraries, art galleries, museums

Air humidification can prevent damage to collectibles caused by the drying and cracking of fibers due to excessively low relative humidity in air-conditioned environments. Many priceless manuscripts, books, works of art, floppy disks, magnetic tapes, and other items housed in museums—without being stored in spaces with proper temperature and humidity control—can easily suffer severe damage. However, the ideal environmental conditions for such items often involve lower temperatures, which can be uncomfortable for visitors. Generally, the lower limit for relative humidity for paper-based collections in museums is 40%; for items like floppy disks and magnetic tapes, which need to be protected from drying out and becoming brittle, the lower limit is even lower—at 36%. Organic collections, on the other hand, require even cooler environments. On the other hand, museum collections are typically rotated between exhibition spaces and storage rooms. It’s important to note that even in environments with controlled temperature and humidity, heat conduction from outside walls or radiant heat from switching lights can still cause fluctuations in the surface temperature of the collections, leading to moisture evaporation and structural damage. Furthermore, when a collection is moved from a cooler storage room into a warmer exhibition space, its surface temperature gradually rises. As a result, internal moisture begins to migrate toward the surface and condense, creating a phenomenon known as "moisture transfer." This process can accelerate the deterioration of the collection. The following temperature and humidity recommendations are suggested for museum environments: