Standardization of Operator Enclosure Air Quality- Rationale for the Amendment to ISO 23875



ISO 23875:2021 was Amended in May of 2022, having received 100% positive votes in the recently completed international balloting process. It is essential for those who will rely upon ISO 23875 and its Amendment 1 to understand the rationale for the Amendment.

Why was Amendment 1 to ISO 23875:2021 proposed?

ISO 23875:2021 required ISO 29463, a specific filter test standard and classification system. Field feedback indicated that most providers are not equipped to comply with ISO 29463. However, they can perform the decay and leak tests otherwise required by ISO 23875 to ensure appropriate filter selection. The primary purpose of the standard is enclosure air quality, which is determined by the decay and leakage tests rather than a specific filter test method.

What does the Amendment do?

The Amendment requires disclosure on the filter label of the filter efficiency at 0.3µ-0.5µ, nominal airflow, and filter restriction. Regardless of the filter efficiency testing method or classification, the requirement is to pass the air quality system tests. Additionally, it removes all references to the filtration standard, ISO 29463.


Does the proposed Amendment maintain the integrity of ISO 23875:2021?

Yes. The objective of ISO 23875 is to provide the means and the methods to develop and validate acceptable air quality inside the operator enclosure on an ongoing basis. Acceptable air quality has low particulate concentration and oxygen sufficient to support mental activity. The focus remains on these objectives.


Does ISO 23875:2021 allow the use of non HEPA filtration?

Yes. While HEPA filters are a good option, the requirement is to pass the decay and leakage tests, which can be done with filters well below the HEPA efficiency level. For clarification:

There are two methods commonly used to quantify filter efficiency.

1. MPPS (e.g., EN1822, ISO 29463)

2. Fixed particle size of 0.3µ-0.5µ (e.g., EN779, ASHRAE 52.2, Mil-Spec. tests, IEST standards, etc.).


Under the first method, HEPA filters begin at an efficiency of 99.95% @ most penetrating particle size (MPPS). Under the second method, HEPA filter efficiency starts at 99.97% @ 0.3µ fixed particle size. Under the first method, Efficient Particulate Air (EPA) filter efficiency is between 85% and 99.95%. Under the second method the EPA range equates to ≥ 94% efficiency at the fixed 0.3 µ particle size. Testing has shown that filters within the EPA efficiency range consistently pass the decay and leakage tests.


It is challenging to correlate efficiency testing at MPPS and efficiency testing at a fixed 0.3µ particle size. However, both approaches provide the test data required to qualify a filter that complies with the ISO 23875:2021 decay and leakage tests.


Who benefits from Amendment 1?

All users of ISO 23875:2021 benefit. It allows for regional and national filter test standards to qualify filters. It opens the market to more suppliers allowing for more competition while maintaining the operator protections afforded by ISO 23875:2021. It is a Win-Win.


Check out the ISEEE online course on how to implement ISO 23875 with Amendment 1. This course will accelerate your understanding of the standard and provide time-saving templates for the required maintenance manual and performance tests.




102 views0 comments