Equipment inside the cleanroom is designed to generate minimal air contamination. Even specialised mops and buckets exist. Cleanroom furniture is also designed to produce a minimum of particles and to be easy to clean. Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded; However, alternatives are available. Cleanrooms are not sterile (i. E., free of uncontrolled microbes) and more attention is given to airborne particles. Particle levels are usually tested using a particle counter
