Source review: October 19, 2026. This overview summarizes the dated primary guidance linked below; it is not a substitute for the current official chapter or a facility-specific SOP approved by the designated compounding professional.
USP surface sampling has minimum frequencies
USP <797> surface sampling is not simply a matter of choosing an interval from a local risk assessment. USP’s December 11, 2023 FAQs, question 108, explain that category-based minimum frequencies replaced the earlier “periodic” approach. A clean trend should not be presented as permission to ignore an applicable minimum.
Category 1 and 2 versus Category 3
The Florida Department of Health inspection guide, revision August 2024, page 6, calls for microbiological surface sampling in classified areas and pass-through chambers at least monthly under dynamic operating conditions. Its Category 3 provisions require at least weekly sampling regardless of how often Category 3 compounding occurs, and sampling before assigning beyond-use dates beyond the Category 2 limits.
The same guide specifies Category 3 sampling inside the primary engineering control at the end of each batch before cleaning and disinfection. For a self-enclosed robotic device, it describes sampling at least daily at the end of compounding operations before cleaning and disinfection. Confirm the applicable chapter provisions and facility setup before implementing this schedule.
USP FAQ 118 separately confirms monthly pass-through-chamber sampling for Category 1 and 2 and at least weekly for Category 3, with the additional beyond-use-date condition. These are minimum requirements in the cited guidance, not interchangeable options.
What the facility must still define
Minimum frequency does not answer every implementation question. USP FAQ 109 explains that the sampling plan must be facility-specific and documented in SOPs. The number and selection of sampling locations depend on the activities in the area; the FAQ does not provide one room-size-based minimum number of microbiological samples.
Have the designated professional identify the applicable compounding category, locations, sampling procedures, timing, documentation and response responsibilities. Keep viable surface monitoring distinct from personnel qualification, viable air monitoring and room certification, even when activities are coordinated.
Action levels are not arbitrary local thresholds
Do not raise an action level to accommodate a contaminated baseline. USP FAQ 111 refers to action levels in the chapter and requires an attempt to identify recovered microorganisms to genus when those levels are exceeded. Verify the applicable current table and response requirements before finalizing an SOP; this overview does not reproduce numerical thresholds or prescribe a remediation procedure.
Where equipment fits
Airflow visualization, nonviable particle measurement and viable surface sampling measure different things. An airflow image or particle count does not establish the microbial result of a surface sample. Equipment selection should follow the facility’s approved monitoring plan and the relevant instrument documentation.
Applied Physics can be contacted about equipment requirements. A product purchase does not confer USP certification, regulatory approval or a guarantee of preparation sterility.
Before adopting a schedule
Use the linked guidance to identify the minimum-frequency issue, then verify the current official USP text and any applicable jurisdictional requirements with the responsible compounding professional. The sources summarized here are dated December 2023 and August 2024; the complete latest chapter text was not independently reviewed for this article. Do not use this overview alone to establish clinical compounding procedures.
