What is a Cleanroom?

Cleanroom are rooms with special filtration to remove particles and dirt from the room. This blog covers: what is a cleanroom, the invention of cleanrooms, how they work, what is a cleanroom classification, and what industries use cleanrooms. It will also cover different types of cleanroom – recirculating cleanroom vs. one pass cleanroom and hard wall vs. softwall cleanrooms. Cleanrooms usually have custom HVAC systems to control temperature, humidity and room pressure. Industries that use cleanrooms include semiconductor, medical device, pharmaceutical , aerospace, USP797 compounding pharmacies and R&D laboratories. Pharmaceutical cleanrooms and medical device cleanrooms are required by FDA to meet CGMP standards.

The HEPA fan filter units in ceiling (Figure 3) remove 99.7% of particles greater than 0.3 microns from the air and push the clean air into the room. The clean air pass thru the room exits thru low wall air returns and pass thru the air return walls back to the negative pressure plenum where the air is cleaned again and re-used. Only HEPA filtered air is allowed to enter the cleanroom.

Cleanrooms are net heat generators due to the friction of air passing at high velocity and volume thru the HEPA filters, cleanroom personnel, lighting, and equipment inside of cleanroom. Most cleanrooms have dedicated AC units (Figure3) that inject cool 55 degree air into the plenum where it mixes with recirculating air to keep the cleanroom cool.

Cleanrooms have gown room / airlocks to prevent dirt from entering the cleanroom every time somebody enters or exits the cleanroom. Only one door of air lock is opened at a time which prevents air from flowing from outside the cleanroom to inside the cleanroom.

Cleanrooms are classified by the numbers of particles in a given volume of air. The FED STD 209E counts the number of particles per cubic foot. The ISO 14644-1 standard counts the number of particles per cubic meter. Other criteria to meet cleanroom class include air changes per hour of HEPA filtered air.

Cleanrooms can be either recirculating or one pass design.

Recirculating cleanrooms are most common because they continuously clean the already clean cleanroom air resulting in less particles in the cleanroom. They are also the only design that allows cleanroom air conditioning and humidity control.

One pass cleanrooms pull air from outside cleanroom, filter the air using HEPA fan filter units, push the filtered air into the cleanroom, then finally exhaust the air back outside the cleanroom. One pass cleanrooms do not have temperature or humidity control. The one pass design it typically used to save money or if the air outside of the cleanroom is already temperature controlled.

Cleanrooms can be either conventional construction, modular or softwall design.

Modular cleanrooms are prefabricated in our factory and then assembled on-site. This allows for faster design and construction than conventional construction cleanrooms. The components are like a LEGO set so they are easily modified or can be disassembled and moved to a new location. Modular cleanrooms can be designed and built in less than half the time of conventional construction (Figure 13).

Softwall cleanrooms use clear vinyl instead of hard walls to keep particulates out of the cleanroom. They use HEPA fan filter units to clean the air and are one pass design. Cleanroom strip curtains are used to prove entrance/exit into the cleanroom. They are not as cleanroom as hard wall cleanrooms as they do provide positive pressure to keep dirt from entering cleanroom. In addition, since they are one pass design softwall cleanrooms cannot offer temperature or humidity control.