When particle instruments are first supplied to customers, they come equipped with caps on the sampling inlet. This is protect against contamination getting into the unit prior to it’s intended use in a controlled environment. It’s been industry standard practice for decades to then CAP particle counters during cleaning and or decontamination processes to protect the counters sampling inlet from liquid and or contamination.
Various different types of stainless steel caps are available (standard, pressure relief, tethered) and others in order to help customers protect their particle counters and get the maximum life out of them. If you have staff that are prone to lose things, then the tethered version (image above) makes sure they can’t lose their caps. They can be easily fitted to ISO probes and they have proven to be a good investment in protecting particle instruments.