Particle Deposition Meters
In a cleanroom floating particles are carried off with air. Particles that can not be carried away will fall on surfaces. Particles larger than 25 μm will fall faster than they can be carried away by the air. Locally it may be possible to deflect a not so large falling particle away from the product.
Falling particles in a cleanroom come from people, generating these particles or carrying them on their clothing or skin surfaces or on surfaces of objects taken in the cleanroom without sufficient cleaning. If not all (especially horizontal) surfaces in a cleanroom are cleaned on a regular base, the number of particles larger than (>) 25 μm will increase in the cleanroom. By operations in the cleanroom, these particles may be moved en they will fall on other surfaces.
Particles between 5 and 25 μm show a similar behaviour as falling particles but a part, in particular the smaller particles, can still be drained. The degree of presence of the larger more or less floating particles can be measured with airborne particle counters.
Measures to lower the level of falling particles have their effect on all particles larger than 5 μm. The product nd*d, in which nd is the number of falling particles larger than d μm per hour per surface unit and d de size of the particle, is a rate for the level of particle deposition and thus the risk of contamination of an exposed vulnerable surface.
Four reasons to measure particle deposition
1. Surface cleanliness
Managing surface cleanliness starts by sampling relevant places close to your assembly site. Monitoring will allow a good prediction and provide tools for improvements.
In order to live up to GMP, the results of the action taken need to be evaluated. Direct feedback is a key feature of the particle deposition monitoring equipment. Measuring what is the impact of the positioning of tools on a work surface can influence in a high degree the deposition of particle on the product made.
3. Cost reduction
Avoiding contamination will result in lower cleaning costs and save not only production time but as well safeguard products and improve on final quality.
The direct correlation between yield and particle deposition can be found thus allowing to go to the point of cost optimation or maximise the yield if required. A new management tool is added.