Frequent or Continuous?
To demonstrate compliance to ISO, frequent monitoring requires sampling at specified time intervals not exceeding 60 minutes during operation. Manifold systems are the least expensive solution and usually installed during the cleanroom construction process. Standalone particle counters may be installed at any time. A manifold system includes either 16 or 32 sampling ports with a single line that connects to a particle counter. The manifold sequentially samples from each port, sends the samples to the particle counter, then repeats the process. However, since a manifold cycles through many sample points, a particle event can go unnoticed if the particle counter is not currently monitoring the appropriate port.
- Frequent Monitoring Solution: Lasair® III 110 Aerosol Particle Counter
Continuous monitoring requires constant sampling. Particle counters constantly gather data, so events are not missed. Sample intervals can be any duration, but shorter sample intervals will give better time resolution. Short intervals will also provide vast quantities of data that can overwhelm a system. Typical time intervals range from one minute to ten minutes. Particle counter choices for these applications are diverse and plentiful.
- Continuous Monitoring Solution: Airnet® II Air Particle Sensor
Takeaway: Choosing between continuous and frequent cleanroom monitoring is a choice of economics and infrastructure. Dedicated particle counters are the best method to detect particle excursions, but at a high cost per sample point. If short-duration events are not critical and there is a greater need for trending, a manifold system can be an effective and economical solution. However, manifold systems cannot reliably transport and count particles much larger than 5 µm.
Look forward to the next blog in this series, which covers the number of monitoring locations required for your clean area. Want to know more tips before buying an aerosol particle counter? Download the full paper here.