Its core principle is to selectively separate solid particles or liquid droplets contained in fluids (including liquids and gases) by means of specific media, namely filter media or filter screens. The filter media feature defined pore sizes: particles smaller than the pores pass through, while particles larger than the pores are retained on the surface or within the media.

History of Filtration

The development of filtration technology dates back to ancient civilizations. Archaeological evidence shows that paper made of plant fibers appeared in China as early as 200 BC, which can be regarded as the embryonic form of early filtration technology. In 105 AD, Cai Lun improved the papermaking process, bringing a phased breakthrough to filtration technology. Early filtration mainly relied on gravity. Driven by growing industrial demands, mechanically assisted methods such as pressure filtration and vacuum filtration were gradually developed. The advent of rotary drum vacuum filters at the start of the 20th century marked the arrival of continuous filtration operations, followed by the development and application of various continuous filtration equipment. Meanwhile, batch filters such as plate-and-frame filter presses achieved new progress through automation upgrades with constantly expanded filtration areas. Mechanically squeezed filters were also tailor-made to meet requirements for low moisture content filter cakes.

Modern filtration technology has been deeply applied across vital economic sectors including water treatment, air purification, chemical engineering, pharmaceuticals and food processing. With advances in material science and intelligent control technologies, innovative filter materials and smart equipment keep upgrading, forming a complete technical system covering microfiltration, ultrafiltration, nanofiltration and reverse osmosis, which delivers precise solid-liquid separation solutions for all industries.

The evolution of filtration technology can be divided into four key stages:

1. Ancient Filtration Technology Primitive filtration methods were mastered in early human history. Natural materials such as cloth and paper were used for basic solid-liquid separation, laying the foundation of filtration technology.

2. Industrial Revolution Era The Industrial Revolution in the late 19th century boosted technological innovation. The emergence of pressure filtration drastically improved filtration efficiency and launched the era of mechanized filtration.

3. Breakthrough in the Early 20th Century The invention of rotary drum vacuum filters at the beginning of the 20th century was a milestone, realizing continuous filtration and laying the groundwork for large-scale modern industrial applications.

4. Modern Technical System Contemporary filtration technology has formed a multi-dimensional technical matrix including microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Widely adopted in water treatment, air purification, biomedicine and other fields, it drives process innovation across industries.

Milestones in the Evolution of Technical Standards

1940: The world’s first cleanroom was built in the United States, marking the origin of the cleanroom technical system. 1950: High-efficiency particulate air (HEPA) filters were invented, establishing core technical standards for air filtration. 1961: The U.S. Air Force issued Technical Order 203, which defined laminar flow cleanroom standards and standardized cleanroom technology development. 1963: The United States issued the military cleanroom standard Federal Standard 209, establishing a full set of specifications for cleanroom technology. 1980s: Research institutions in the U.S. and Japan independently developed ultra-low penetration air (ULPA) filters capable of capturing 99.99% of particles as small as 0.1 μm, ushering in a new phase of precise submicron filtration. 1987: Federal Standard 209C was released, expanding the original four cleanliness classes (Class 100, 1,000, 10,000, 100,000) into six grades (Class 1, 10, 100, 1,000, 10,000, 100,000) for more refined cleanliness classification. 1992: Federal Standard FED-STD-209E was issued, reforming cleanliness measurement units from imperial to metric and adding seven M-series grades (M1–M7), creating a technical system aligned with international norms. 2001: The United States officially adopted the international standard ISO 14644, signifying the global unification of filtration technical standards.