10 Aspects of Clean Room Design

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Jul 27, 2012

Sensitive processes like scientific and pharmaceutical research, microprocessor manufacturing, and culture development require sensitive environments. Critical environments, also called clean rooms, can provide for those environments, but they have to be designed very carefully to carry out such technical functions. Clean rooms are complex and can be costly, so they have to be done right.

Below are 10 aspects of that design process that could be considered.

1. Clean room designs should take into the account of staff and material movement. That means critical processes such as pharmaceutical production should be isolated from major pathways in the layout. These processes should have single access and be out of the major pathways to prevent cross contamination.
2. Clean room classifications are important and will determine the overall design and requirements of the clean room. The more sensitive the processes you need to administrate, the more stringent standards required for clean room cleanliness. Classes range from 1 to 100,000, with the lower numbers indicated higher standards in particle removal. For example, a class 100 clean room requires 3,500 particles/cu ft or less at 0.1 microns and larger, 750 particles/cu ft or less at 0.2 microns and larger, 300 particles/cu ft or less at 0.3 microns and larger, 100 particles/cu ft or less at 0.5 microns and larger, and 24 particles/cu ft or less at 1.0 microns and larger. At higher classes, the requirements are lower, at lower numbered classes, the requirements are higher. Knowing the sensitivity of your project and how it corresponds to the clean room class requirements is important in designing a critical environment.
3. Space supply airflow figures in terms of the clean room's class of cleanliness and the amount of traffic and particles that will be coming in through the room. A higher value indicates a higher trafficked area and should be considered when designing a clean room.
4. What sort of space pressurization will your clean room use? Positive pressure is useful for pushing air out of the room and keeping the contamination out. It pays to think about pressure differentials between rooms as well, as a certain differential will not only have consequences on cross contamination, but energy used to maintain pressures and the difficulty of opening and closing doors.
5. Space exfiltration flow has to do with air moving from room to room when doors are opened between rooms of various pressure differentials. Which direction is this air moving? Which direction should it move? A good clean room design should have carefully controlled air flow.
6. Space air balance has to do with the overall movement of air between rooms that takes into account present air, air leaving, and air coming into the rooms. This variable plays a role in the way clean rooms are designed as well.
7. HVAC systems can be used to manage temperature and humidity. Unless a clean room process requires a higher temperature, a lower room temperature should be planned on to account for present staff and their warm clothing (full coveralls, hoods, goggles, masks, and gloves). Humidity on the other hand should kept to a certain degree where particles aren't kept stuck to surfaces due to higher electrostatic discharge, but not too high where microbes/bacteria can thrive. HEPA filters with laminar air flows can take care of particles as well.
8. Mechanical system layout figures into the cleanroom design. This aspect can be affected by such variables as space availability, available funds, project requirements, classification level, energy, building codes, and local climate.
9. Heating and cooling calculations for the clean room take into account the following considerations: required climate, air movement, humidifier manifold heat, process load, and recirculation fan heat.
10. Finally, how much space will be needed for the mechanical systems that will keep the clean room clean? What sort of classification of clean room will be built and how clean must it be? The design may have to make room for machinery depending to needs: filters, heating/cooling coils, fans, sound attenuators, return fan, relief air section, outside air intake, humidifiers, discharge plenums, and more. As you can see, clean rooms are quite complex and require much deliberation in design.

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