A cleanroom provides a controlled, isolated environment for handling contamination-sensitive substances or for protecting the exterior environment from dangerous substances in the controlled area. The density of sub-micron and larger airborne particle contamination inside a cleanroom is kept within tightly controlled limits by forcing clean, filtered air into the cleanroom. Controlling particulate contamination is a process, not an event. Contaminants are generated continuously by people, processes, facilities and equipment and must be continuously removed from the cleanroom. The allowable level of contamination is dictated by specifications for the operations being performed. In the US, particle counts per cubic foot are commonly given as “class ratings,” such as “Class 1000” specifying fewer than 1,000 particles, with a size greater than .5 μm per cubic foot. ISO standard 14644-1, however, provides more precise standards but is often used interchangeably in the US. Contamination control requires controlling the total environment. Air flow rate and direction, pressurization, temperature, humidity and specialized filtration all need to be tightly maintained to remove particles from the cleanroom. Particles sources must be eliminated whenever possible. Positive pressure modular cleanrooms provided by Terra Universal typically use ceiling-mounted self-powered Fan-Filter Units (FFUs) to force HEPA- or ULPA-filtered air into the cleanroom. This creates an internal air pressure greater than ambient pressure, which reduces particulate intrusion around doors, and minor un-sealed areas in walls, ceilings, etc. Wall venting near floor level exhausts cleanroom air with the particles it carries into the external environment and promotes laminar flow of incoming air. The ability to remove particles and thus create a particulate-controlled environment inside the cleanroom is measured by the number of air changes per hour; the more clean air, the cleaner the cleanroom. Basically, a positive pressure cleanroom protects the internal environment. In a given cleanroom, cleanliness can generally be increased by simply adding more FFUs, and thus filtered air, in the correct locations. Positive pressure can be built with hard walls made of solid plastic or steel, or soft walls made from flexible plastic strips and curtains. In hardwall cleanrooms, temperature and humidity can be controlled to provide human comfort, protect processes and prevent static charges by adding air conditioners, humidifiers and dehumidifiers. Negative-pressure modular cleanrooms provided by Terra Universal are designed to keep contaminants from entering the external environment. A common design uses exhausting FFUs, or air handlers, and HEPA filters to remove internal air. The cleanroom's in-room processes contaminate the air, that is then exhausted to a safe location. This exhaust system creates a negative pressure inside the cleanroom that draws external air into the cleanroom either directly or through filters. A common application for this design is a powder filling operation. A negative pressure cleanroom, then, protects the external environment but not necessarily the internal area. Positive/negative pressure modular cleanrooms provided by Terra Universal, a more complex design, typically use FFUs to inject clean air into the cleanroom and exhaust contaminated cleanroom air into a buffer area. An air-handling system then removes slightly more air from the buffer area than is supplied by the FFUs, thus creating a negative pressure with respect to both the cleanroom and the external environment. This negative pressure prevents cleanroom contaminates from entering the external environment and also prevents external particulates from entering the cleanroom. A positive/negative pressure cleanroom, then, protects both the cleanroom and external environments.

Hardwall modular cleanrooms provide a rigid wall structure and a completely enclosed cleanroom with air vents to exhaust air. These cleanrooms hold higher pressure differentials, which is important to provide differing cleanliness levels in different areas (and which is required to meet FDA 797 requirements). Negative and positive/negative pressure cleanroom designs require hardwall cleanrooms, as do A/C and humidity control cleanrooms. Terra Universal fabricates hardwall cleanroom walls from acrylic, static- dissipative PVC, polycarbonate, and polypropylene (all in various colors) with frames of powder-coated steel. In addition, Terra offers BioSafe hardwall cleanrooms fabricated from 304 or 316 stainless steel. Softwall modular cleanrooms use a simpler steel frame structure to support flexible PVC (or non-out-gassing Polysym) curtains cut a few inches above the floor to provide an exhaust vent. Softwall cleanrooms provide only the lowest of positive pressures and are typically used only in lower cleanliness ratings such as Class 1000, 10,000 and 100,000. Because these cleanrooms offer less control over air flows, temperature and humidity control are normally not provided. Smaller softwall cleanrooms can be fitted with casters. Softwall cleanrooms are generally not suitable for complex, multi-room designs and long spans.

Although both types of cleanroom can be built to meet the same air-change-per-hour standards, hardwall cleanrooms offer a more complete barrier to particle intrusion and more control over atmospheric temperature and humidity than is possible with softwall cleanrooms. Probably the most important difference in many applications, is that a hardwall cleanrooms can hold a significant positive pressure, which prevents particulate intrusion. Since softwall cleanrooms generally have a perimeter air gap, they can maintain very little positive pressure and no negative pressure differentials. Hardwall cleanrooms offer somewhat less turbulent air flow since the walls are fixed and do not move as is possible with softwall cleanrooms. Plus, it is definitely easier to clean hard walls than curtains and strips. Up to a reasonable size, softwall cleanrooms can be mounted on casters, which makes them mobile. Hardwall cleanrooms are fixed in place but can be disassembled, moved and reassembled. Finally, softwall cleanrooms cannot be secured against unauthorized entry.

Ideally, the ESD properties will last as long as the tile does, but sometimes accidents happen. However, SelecTech stands behind our flooring products. When installed and maintained according to our installation and maintenance guidance, we provide an extensive warranty. For example, a 10-year warranty against wear on our ESD flooring, as well as a lifetime performance warranty is offered to our customers. Additionally, our interlocking flooring allows for easy replacement of damaged tiles to reinstate the ESD properties without removing large sections of the floor.