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Combined Interpretations of the 2003, 2009, and 2016 Standards that apply to Volume 1 of the 2016 TNI Standard


MODULE 5: MICROBIOLOGY TECHNICAL REQUIREMENTS
Section: 1.7.3.7

Question:  What does "autoclave maintenance... shall include a pressure check" mean?  Does that specifically mean that the pressure relief valve shall be checked and documented?  If would be extremely helpful if these sections could be written more specifically.

TNI Response:  Since PV=nRT, checking the temperature and assuring no leaks (so that V is constant) is sufficient to meet the requirements of the standard. Another suggestion: A note could be made in a logbook indicating that seals were checked and no cracks were found.  The 2016 standard added in the PV= nRT language and called it sufficient.

 

Question:  This section states that "... When it has been determined that the autoclave has no leaks, pressure checks can be documented using the formula PV = nRT."

Every resource we can find states that saturated steam does not behave as an ideal gas and we are unable to match results from this formula to actual observed results.

Is this portion of this requirement still considered to be realistic and if so, are there resources available to clarify how this should be used and reported?

TNI Response:  Since PV=nRT, checking the temperature and assuring no leaks (so that V is constant) is sufficient to meet the requirements of the standard. Although saturated steam does not behave as an ideal gas, if the temperature is checked and the volume is constant and there are no leaks, the pressure is verified.

The Standard does not require this approach but provides it as an option for laboratories who are performing pressure checks on their autoclaves.

In addition, V1M2 5.5.13.1.a and V1M2 5.5.13.1.b of the 2016 TNI Standard are applicable to this SIR.

The second part of the submitter's question is asking for a "how to" rather than an interpretation.