The Masy Blog

Steam Quality Testing: What You Need To Know

Estimated reading time: 4 minutes

Steam quality testing should be performed as part of the initial validation of the sterilizer. It should also be performed as part of the annual re-qualification of the sterilizer. Testing should also be performed if there is any indication of deteriorating steam quality or if there are any modifications or repairs to the steam distribution system. Over the years, customers have asked us about various aspects of steam quality testing. This article covers some of the most common or most interesting questions, and our answers based on over 35 years of biopharma validation experience.

  • When performing steam quality testing, what is the consensus regarding when steam quality samples should be collected? 
  • We typically recommend gathering the “first pulse” of steam (e.g. gather samples as soon as the steam valve opens). This means a new autoclave cycle is initiated for each individual sample collection. However, some autoclave manufacturers recommend collecting steam quality samples back-to-back during a single extended cycle (e.g. collecting samples back-to-back after the initial pulse has been purged through the system).For reference, EN-285 has the following verbiage regarding sample collection:
    • 1.3.8 (non-condensable gas) “…when the steam supply to the sterilizer chamber commences….”
    • 2.3.12 (dryness) “…when the steam valve connected to the sterilizer first opens…”


  • Non-condensable Gas Tester (L), and Dryness Tester (R), two pieces of equipment used in steam quality testing.


    We have spoken with Keith Shuttleworth & Associates, manufacturer of the most used kit for performing the testing about this topic. They mentioned performing multiple tests back to back during a single cycle. The important thing to consider is that for best results, you want to take the samples while the autoclave is running to capture the system in its normal operating state.  If you took samples with the autoclave in standby or while steam wasn’t actively flowing, there could be a small buildup of non-condensable gas and condensate that could impact the readings.  For the most conservative route, you could take the samples over multiple different cycles to show consistency, but as long as the steam supply header is maintaining a stable pressure, there should be little to no change based on the runs getting performed back to back or in different cycles.

  • If I have multiple steam sterilizers do I need to test each sterilizer port for steam quality?
  • It is important to test all steam sterilizers unless more than one sterilizer is on a steam manifold off a steam header, then it is not necessary to sample all of the sterilizers - take the samples from the sterilizer furthest away from the boiler. See HTM0101 Part C Paragraph 3.138:“Where more than one sterilizer is supplied from the same steam manifold, steam samples should be taken at the sterilizer furthest downstream from the boiler. It is not necessary to sample the steam at each sterilizer.”A Vacuum Leak Test should be done prior to any penetration testing, including Bowie-Dick to make sure that all seals are tight, and no slow leaks are present, which would render other tests inaccurate. If pressure is confirmed stable in the beginning, comparison tests become far easier, and the engineer won’t need to waste valuable time and resources trying to troubleshoot.
  • What are “pressure pulses” and how do they apply to steam quality testing or autoclave/sterilizer qualification?
  • Adding pressure pulses may be necessary to make sure that all load items equilibrate to the correct temperature and pressure to ensure effective sterilization. If cycle development showed good results, this step may not be necessary. Four pulses are sufficient to achieve sterilization in most scenarios. However, if sterilization is inconsistent, you may need to add additional pressure pulses, or increase vacuum/negative pressure. While vacuum pressure resolves most of these issues, positive pressure pulses are occasionally required depending on the equipment and load items used.
  • Are changes to autoclave validation or steam quality testing SOPs necessary when transitioning from non-GMP to GMP production?
  • While GMP compliance doesn’t require all SOPs to be rewritten, be sure to systematically evaluate existing processes to ensure they align with any significant changes to daily operations including changes to load items or sterility requirements and regulations. All SOP changes should be thoroughly documented, and all relevant employees trained prior to using the new procedures.

Steam quality testing is an essential part of ensuring autoclave/sterilizer performance and should be performed when new equipment is installed, when changes are made to the equipment or load items, or when there is an indication that sterility performance is declining. Annual requalification is recommended to ensure that performance issues are identified and corrected early, preventing biological or chemical contamination of loads. Read our steam quality whitepaper for more information or contact us with any questions you may have.