If the phrase you’re abbreviating is plural, make that clear in the acronym by adding an s.
We then tested for chemicals of potential concern (COPCs).
You can make any acronym plural by simply adding an s, even if the acronym itself ends in an S.
Applications are keyed by universial well identifier (UWI). You can enter multiple UWIs in this field.
Anyone directly and adversely affected by an application may file a statement of concern (SOC). All SOCs are evaluated based on the following criteria.
The company uses two AWSSs [aboveground synthetically lined wall storage systems]…
Note that units of measure are never pluralized when abbreviated.
The pipeline is 5 metres long.
But: The pipeline is 5 m long.