by Raffe Khazadian
Clean rooms are complex to design, as they provide a space where the particulate count in the air is regulated. They offer an indoor environment unique to any other indoor environment, and with it, pose some unique design challenges.
Clean rooms are classified by the International Organization for Standardization (ISO), which allows rooms to be classified by restricting particulate count ranging from ISO 8 (Class 100,000) down to ISO 3 (Class 1). This classification governs the particulates allowed to infiltrate the air.
Depending on clean room function, the space design and layout can vary. However, most clean rooms have similar distinct design features for successful operation, including:
• Gowning rooms. This space (typically of higher classification) allows an employee to change into the proper attire for the clean process inside.
• Ante rooms are intermediate rooms that allow for stepping down the ISO classification for entering and exiting the clean room.
• Air locks are similar to ante rooms and are designed for people or equipment.
• Pass-through rooms are used for samples moving from one room to another of different classifications. These can be bigger for wheeled equipment as well.
• Windows are designed in clean rooms to make sure the people working inside are safe. Windows are detailed to be flush glazed to avoid any horizontal surfaces that might create an extra cleaning burden.
Many industries use clean rooms, including pharmaceutical, micro-electronics, semiconductor, and medical device, to name a few. Clean rooms for the pharmaceutical industry have a high cost per square foot, mainly due to the use of 316 stainless steel for corrosion resistance, among other reasons. The pharmaceutical industry often requires decontamination of clean rooms, which is typically done by vaporized hydrogen peroxide or chlorine dioxide. Both methods tend to corrode some metals, making stainless steel a necessity.
Clean rooms require specialized materials and systems that drive up the building cost, including:
• Flooring is commonly specified as poured-in-place epoxy, urethane, or sheet vinyl with heat-welded seams. These types of floors allow for a continuous floor system with an integral cove base.
• Walls can be coated with fiber-reinforced plastic panels for a more durable, yet expensive, solution. A less expensive option is epoxy paint.
• Chlorinated polyvinyl chloride (CPVC) is a type of plastic panel used inside clean rooms on the walls and ceiling that allows for corrosion and chemical resistance.
• Ceilings are typically constructed of gypsum wall board or a clean-room-rated ceiling tile and grid system. These tiles are sometimes made of vinyl-faced gypsum wall board, which makes them heavier than normal ceiling tiles and require hold-down clips to prevent the exfiltration of air.
• Lighting typically consists of lensed and sealed fixtures. These specialized fixtures are designed for wash-down procedures and to prevent the exfiltration of air.
• Devices are typically manufactured of higher-grade materials, such as stainless steel, and require additional measures to keep clean and prevent exfiltration.
• High efficiency particulate arresting (HEPA) filtration is high performance filters used to reduce the particulate count in the air. These filters are subject to specialized cleaning and changing, sometimes referred to as bag-in/bag-out. This can be done inside the clean room, remotely above, or at the air handling unit.
• Specialized clean room furniture is typically made of stainless steel and/or high-grade plastics.
• Supply and exhaust air (the mechanical system) are the main cost drivers for clean rooms. Air handling is where the big dollars are spent. Costs vary widely, depending on ISO classification, temperature control, pressurization, and relative humidity requirements.
Each of these features contributes to the increasing expense of designing and constructing a clean room. Typically, construction costs for an ISO 8-7 clean room can range from $250/sf to $1,500/sf or more. Working with an experienced clean room lab designer can help a company determine its design priorities and manage the costs of building a clean room.
Raffe Khazadian
Raffe Khazadian, AIA, NCARB, LEED AP O+M, CDT, is an associate principal at TRIA, an architecture firm located in Boston.
