How to Validate an Autoclave1

IntroductionThere is an array of qualification tests that can be conducted to validatean autoclave. Many laboratories validate autoclaves by simply usingbiological indicators (BIs). For some labs, however, a simple validationwith BIs is not enough and a more elaborate validation process mustbe followed. These labs typically require installation, operation, andperformance qualifications (IQ/OQ/PQ) to help comply with the currentUSA and International Standard for steam sterilization as set forth inISO 17665.In this eBook, we will explain a variety of validation tests you may needto perform in order to properly and effectively validate your autoclave.How to Validate an Autoclave2

Table of Contents4 / Calibration8 / Cycle Development10 / Installation Qualification13 / Operational Qualification17 / Performance Qualification21 / Steam Quality Testing27 / Factory Acceptance Testing31 / Simple Validation ProcedureHow to Validate an Autoclave3

1. Calibration“Calibration” is a word that is frequently used in the steam sterilization industry.At its very basic premise, calibration is bringing the response of a sensor (e.g.transducer, thermocouple, etc.) to within a specified range relative to a primaryreference standard. For example, an autoclave’s chamber temperature probe’sresponse can be compared to a previously calibrated device, or “standard”,whose response is traceable to a national reference standard, maintained inthe United States by the National Institute of Standards and Technology (NIST).How to Validate an Autoclave4

Why Calibrate?The short answer is calibration ensures consistent results from a process. Steam sterilizationefficacy is highly dependent upon actual temperature. For example, if a steam autoclave is runningat 120 C for 15 minutes, the theoretical lethality of that cycle is only 82% of a cycle running at122 C for the same amount of exposure time.Since most laboratory autoclaves do not require temperature to be accurate to better than 1 C,this variability can be more common than one would think. If your temperature transducers arecalibrated, this problem will diminish.Equipment Required to CalibrateThe proper way to calibrate an autoclave is with the use of a NIST-traceable device (standard) suchas a dry block, oil bath, or temperature probe. If using a dry block or an oil bath (pricing starts atapproximately 1,250) make sure it is designed to control to a constant temperature ( 0.1 C). If thedry block or oil bath is not NIST-traceable, or its calibration has expired, then use a NIST-traceabletemperature probe (cost is approximately 500) with 0.1 C minimum accuracy.Note: As a rule of thumb, the standard should be five times as5xaccurate as the device being calibrated. Therefore, when calibratinga temperature probe with a desired accuracy of 0.5 C, thecalibration standard should be accurate to 0.1 C.If the above-recommended equipment is not available, you can use boiling water to help calibrate the autoclave’s temperature sensors. Boiling water can act as a constant-temperature (i.e.100 C/212 F) bath that is somewhat near sterilization temperature. However, if the facility isn’texactly at sea level then boiling water isn’t necessarily going to be 100 C/212 F. Check the atmospheric pressure in your area (obtained online at or use an absolute pressuremanometer (mercury column or electronic) to obtain the exact pressure reading, then calculate theactual “pressure corrected” boiling temperature of water by using this steam table: ( sat.cfm). If you place your sensor into boiling water (notin contact with the bottom of the vessel holding the water) and it isn’t within 1 C of the theoreticaltemperature then you will need to carry out a calibration.How to Validate an Autoclave5

Calibration MethodsCalibration instructions can vary by the number of calibration points measured (i.e. 1-point, 2-point,or 3-point). What is the difference?Single Point CalibrationA single point calibration is valid only within the accuracy at that specific point. When sterilizing at only one temperature, say 121 C/250 F, this is not too much of a problem, although youhave no idea what is happening in any process excursions to higher or lower temperatures.Two Point CalibrationSome calibration instructions recommend taking two measurements and calculating theslope (gain) and y-intercept (zero offset). Using two points for calibration is relatively fast andconvenient; however, two points define a straight line and reveal nothing about any non-linearity in the probe’s reading. Also, any errors in the two measurements are not going to beevident.Multipoint CalibrationA multipoint (more than two point) calibration will indicate if the probe is behaving in a nonlinear manner, which could be a good reason to replace it, and allows any measurement errorsto be averaged out over the greater number of points. These instructions suggest taking threeor more measurements and performing a linear regression to get the slope and y-intercept.Any multipoint calibration should be done with points both outside the working range of thesterilization cycle(s) you will use. For example, a lab running at 121 C (and only 121 C) shouldcalibrate at 116, 121, and 126 C or at 116 and 126 C for a two-point calibration. This allowsthe response of the measurement and control system to be considered. If the lab is runningcycles over a greater range, calibration should start and finish 5 C below the minimum temperature and 5 C above the maximum temperature used. A good rule of thumb is to calibrateagainst at least the number of degrees in C plus one. So, if you run cycles at three differenttemperatures (e.g. 115 C, 121 C, and 134 C), you would make calibration measurements atfour points (e.g. 110 C, 120 C, 130 C, and 140 C.How to Validate an Autoclave6

Sample Calibration Procedure for an Autoclave1. Record the as-found calibration data (zero and gain) for each sensor to be calibrated.2. Using appropriate caution (shut the steam off and wait for the pressure to go tozero!),remove the sensors to be calibrated from the sterilizer, leaving their cablesconnected to the control system.3. Set the zero and gain to 0 and 1, respectively.4. If using a NIST-traceable dry block or oil bath place the sensor in the dry block oroil bath.5. If using a NIST-traceable temperature probe, place the temperature probe into acentral position in the dry block or oil bath and the sensors as close to it as possible.6. Measure at the selected temperatures and record the standard and transducer dataYou should wait for at least one minute at each temperature to allow themeasurement to stabilize. Don’t rush this step.7. Do a linear regression of the data collected. This is straightforward in Microsoft Excel[intercept() and slope() functions] with the standard’s data on the y-axis and thesensor’s data on the x-axis.8. Do a correlation as well [correl() function]. It should be at least 0.999999 (i.e. avery straight line).9. Enter the zero and gain values to the sterilizer controller to enter the calibration.10. Verify the calibration using at least one point like your process temperature. If more than oneprocess temperature, then verify at each one. Then you will have an exact statement of theaccuracy of the sensors.11. Re-install the sensors in the sterilizer.How to Validate an Autoclave7

2. Cycle DevelopmentCycle development is performed to provide you with a sterilization process (i.e. cycletype, sterilization temperature, sterilization time, etc.) that can be validated. Ideally,cycle development should begin before the sterilizer is purchased, since the cycle typeswill affect the type of autoclave you need, and changes in the field after installation aregenerally difficult and expensive. At the very least, cycles should be developed prior toperforming a full validation of the autoclave and, more specifically, before PerformanceQualification (PQ) validation.It’s worth pointing out that in most laboratories cycle development isn’t required or hasalready been performed by others in the lab. Cycle development is most commonly usedfor biotechnology, pharmaceutical, or medical device companies that are regularly validating their autoclaves and/or sterilizing new or unique loads.How to Validate an Autoclave8

Selecting a Sterilization CycleRefer to the flow-chart below to determine which cycle type is best for your load.Unsterile LoadIs it liquid or doesit contain a liquid?Can air be removedeasily/are there norestrictions on airremoval?NoYesIs the containerflexible with residualair inside?NoUse PrevacuumCycleYesNoDoes the liquid have atendency to boilover easily?YesYesUse Steam-Air MixtureUse Air OverpressureNoUse LiquidCycleUse GravityCycleOnce the cycle type is determined you must decide on the key cycle parameters:sterilization temperature and sterilizer time.The vast majority of loads sterilized in the laboratory setting are sterilized at 121.1 C/250 F for30-90 minutes. For loads that are sensitive to heat, contact your autoclave validation expert foradvice on calculating your sterilization time using the F0 relationship.Once you have determined your cycle type and parameter, you must validate the cycle to ensurethe load will be sterile. These test cycles should be loaded in a way that is representative of theactual load to be sterilized. It is recommended to run your test cycles at half of the desired sterilization time (this is referred to as the “half-cycle” method).Sterility testing is confirmed with the use of biological indicators (BIs). The most common testorganism for steam sterilization is Geobacillus stearothermophilus. BIs are placed in intimatecontact with the load and are placed throughout the chamber. Typically, at least 10 BIs are used percycle. If all BIs show no growth (i.e. all the bacteria are destroyed) in three successive cycles, youhave validated the cycle.How to Validate an Autoclave9

3. Installation Qualification (IQ)Installation Qualification (IQ) provides documentary evidence that the equipment hasbeen built and installed to specification, and that all supporting services (i.e., utilities suchas electricity, water, and steam) are available and connected properly. The IQ processmethodically documents all aspects of the installation, the machine components, and anytesting equipment used to provide a complete, closed-loop assessment. In addition, IQincludes NIST traceable calibration (see above) verification of the unit’s criticalcomponents.How to Validate an Autoclave10

Equipment ProcurementIQ begins before you issue the purchase order for the autoclave. Completing a successful IQ is theresult of careful planning and there should be no surprises when the unit arrives at your facility.Naturally, what you ordered and what you receive should match.IQ is typically carried out concurrently with installation or soon after installation at the user’s facility.The IQ is performed by following a specific IQ protocol tailored for each piece of equipment.Equipment InstallationInstallation has requirements that are unique to each machine, or at least should be treated thatway. As part of IQ, these requirements must be verified. They include:UtilitiesElectrical: voltages, current, fusing, correct number of phases, and three-phase configurationCompressed air: pressure (static AND dynamic), flowWater: pressure (static AND dynamic), flow, temperature(s), purity(ies), dissolved gas contentSteam: pressure, purity, pipe insulation, pipe size and peak flow rateDrain: capacity, temperature toleranceInstallation AreaDimensions: including space to allow serviceFree-standing or through-wall mountingBiosafety barrierSeismic anchoringLeveling: for sterilizer performance and to align with delivery cart for removable load carriagesAn IQ should list the requirements and provide documentation of the presence and adequacy ofeach utility and feature listed above (if so furnished).How to Validate an Autoclave11

CalibrationCalibration requires standards that are traceable to the standards maintained by the United StatesNational Institute of Standards and Technology (NIST). In other countries, traceability is to be to thatcountry’s national equivalent of NIST.Transducers and SensorsFor autoclaves, this means that a pressure standard and a temperature standard should beavailable, as well as a means of providing stable pressure for calibrating the pressuretransducer(s) and a dry block or oil bath for calibrating the temperature transducers.Optimally, a calibration standard should be five times as accurate as the device being calibrated needs to be. For a 0.5 C accuracy on the sterilizer, the standard should have anaccuracy of 0.1 C. Details of the calibration depend upon the sterilizer’s controls systemand how it handles calibrations. Generally, at least a three-point calibration is required,with more points providing a better indication of the linearity of the system. The goldenrule of calibration is, “If you do it fast, you get to do it twice.” So waiting for a stable valueis key in a successful calibration.TimeAnother aspect of calibration is that of the internal clock of the sterilizer. The standardsrelated to steam sterilizers generally have accuracy requirements for the process controlclock(s) in the controller. Testing is straightforward, since NIST has a dial-in phone number(303-499-7111) that tells you the national standard time on a one-minute interval, providingyou with 1 second accuracy. This level of accuracy is adequate for any laboratory autoclave. Measurements at either end of a 24-hour period would be acceptable to any audit.A thorough IQ will enable you to have confidence in your autoclave, and more importantly,documented proof of its ability to carry out the task at hand, not just because themanufacturer tells you so, but also because it has been demonstrated in place.IQ is a critical part of the process for fully commissioning an autoclave andputting it into its appointed use.How to Validate an Autoclave12

4. Operational Qualification (OQ)Operational Qualification (OQ) verifies that the autoclave meets the desired and intendedperformance standards of the lab. OQ testing examines the autoclave’s ability to run thesterilization process correctly and repeatedly while also responding appropriately to errorconditions. OQ testing typically includes the following tests:Empty chamber temperature mappingSimulated load chamber temperature mapping and, if required, verificationof sterilization efficacy using biological indicators (BI)Alarm conditions and expected resultsHow to Validate an Autoclave13

Equipment Capabilities and SpecificationsIn general, the operational requirements for a sterilizer are detailed in a User Requirement Specification (URS). The URS defines the required performance, parameter limits, accuracy, ancillaryfunctions, and standards to which the equipment’s performance must meet. It is the basis ofOQ and can be written by the customer or may be the manufacturer’s specification that the useraccepts.Autoclaves have specific critical process parameters:Temperature set point range and controlTemperature uniformity throughout the chamber and loadPressure range and controlFor prevacuum sterilizers: air evacuation capability, including depth and control of vacuumsetpointsFor any sterilizer: the capability to achieve saturated steam pressures given thetemperature setpoint and control rangeIt may also include evacuation and pressurization rate controlExposure time (and other dwell phase) controlSuccessful cycle execution requires that these parameters are achieved repeatedly and with predefined precision. If the machine must comply with a specific standard (ISO 17665, PDA TechnicalReport 1, PDA Technical Report 48, EN 285), the accuracy and precision of the process parameterswill be specified in the standard.Equipment TestingOQ validation generally includes both empty chamber and loaded chamber temperature mappingfor all cycle types that the facility runs (e.g., gravity, liquid, pre-vacuum, etc.). If an autoclave hasthe capability to run a cycle but it is not currently used, the facility does not have to test it since thevalidation for that cycle can always be run at a later date.How to Validate an Autoclave14

Empty Chamber TestingEmpty chamber temperature mapping is performed to verify and document that the temperaturerange delivered throughout the empty autoclave is within required specifications. Interestingly,temperature mapping an empty chamber can create more of a challenge than testing a fully-loadedchamber because the load’s thermal mass aids in providing temperature homogeneity and limitingovershoot.Empty-chamber testing is done with temperature datalogging probes. Temperatures should bemeasured at a minimum of five locations in the chamber (plus at a point adjacent to the controllingtemperature sensor in chambers up to 800 liters). More sensors provide a more-detailed analysis oftemperature profile.Examples of acceptance criteria are:Chamber temperature -0/ 3 C relative to setpointChamber temperature range over all dataloggers at any given time 2 CPressure datalogging should also be performed only if pressure is a controlled parameter.Simulated Load TestingOQ validation must also test simulated loads that mimic the real loads a laboratory plans to run.These loads may be solid, liquids, glassware, medical devices, in short, anything that wouldnormally be sterilized. For simulated load testing, ensure that at least three of the items in eachload are being monitored for temperature and biological indicator (i.e. place the probe and BI rightnext to or on top of the load).Diverse items processed in a specific cycle type may be tested together, however, their temperature and indicator (see below) data should be evaluated independently. Therefore, if mixed loadsare to be tested, at least three of each item type should be included, and arrayed throughout thesterilizer chamber, not all adjacent to one another.Simulated load testing may also include biological and/or chemical indicator testing. For overkillcycles, half-cycle testing (the cycle has exposure duration of half the normal exposure time)should be carried out for these cases. Biological indicators must have a 106 population of G.stearothermophilus spores for validation testing of steam sterilization. If chemical indicators areused, a Class 4 or 5 indicator is required. Class 6 indicators are only suitable for full-cycle testing,since they are not expected to show a complete cycle in less exposure time.How to Validate an Autoclave15

Alarm TestingHere is sample list of alarms that should be tested during an OQ validation:Alarm/InterlockActionExpected ResultsRecycle AlarmSimulate recyclealarm (Alarm occurswhen temperaturefalls below sterilization temperaturesetpoint for 1 minute or more duringthe sterilize phaseof a cycle)Buzzer sounds,alarm messageprinted, and steamsupply to chamberis shut off andchamber exhaustsOver Temperature AlarmSimulate overtemperature alarm(Alarm occurs whenchamber temperature exceedssetpoint by x C)Buzzer sounds,alarm messageprinted, steamsupply to chamberis shut off andchamber exhaustsTime Limit AlarmSimulate time limitalarm (Alarm occurswhen temperatureis not achievedwithin 1 hour ofcycle start)Buzzer sounds,alarm messageprinted, steamsupply to chamberis shut offand chamberexhaustsMethod & ActualResultsThe method used to activate the alarm must be documented and should simulate the process errorthat would cause it to take place. The actual result must be identical to the expected result in orderfor it to “pass” the OQ validation.Ancillary Items to TestOther unit-specific items that should be tested include, but are not limited, to:Switches to prevent steam from being admitted to the chamber with the door unsealedInterlocks to ensure that, in a double-door unit, both doors cannot be opened at the same timein normal operationFor units with dual transducers, the transducers must read within a specified amount of oneanother during exposure phaseOperational Qualification provides documented proof that the autoclave can execute the requiredprocesses and that its safety and ancillary features work properly. These capabilities must bedemonstrated in the unit’s final location ofHow to Validate an Autoclave16

5. Performance Qualification (PQ)Performance Qualification demonstrates that the autoclave not only runs the requiredcycles, but provides the required result: sterility. The PQ process involves testing theloads that must be successfully sterilized in the autoclave. The prerequisites for PQare successful IQ and OQ tests.How to Validate an Autoclave17

Sample Test ProtocolPQ is comprised of at least three repeated tests for each defined load. The critical aspect of thetests is to validate sterility in each of the loads. Each load type will have its own challenges so it’simportant that each is specified with information such as: number and type of objects being sterilized, sterile barrier material used, and in certain cases, orientation of the objects being sterilized inthe autoclave.Here is a sample PQ test protocol:1. ObjectiveThe Objective is to prove sterilization of the specified load. The sterility assurance level may derivefrom a standard, from a client SOP or specification, or from a manufacturer’s specification. Specificcitations to any of these should be made in this section.2. Procedure or SetupThe Procedure or Setup explains how to setup and execute the test. The followingspecifications should be noted here:The type of cycle (vacuum, gravity, liquids, air-overpressure, low temperature, etc.)including all critical parametersAny equipment needed for the testThe number and location of each item in the loadIf a mixed load is to be run, the number of each item and the items’ locations shouldbe specifiedLocations of the indicators and datalogger probes – these should be placed in“worst-case” locations in the load to provide assurance that the entire load is sterilizedSterile barrier materials or vessel covers (like aluminum foil for flasks), as well astheir application to the items closed by themA step-by-step listing of how to carry out the test3. Acceptance CriteriaThe Acceptance Criteria section lists the required result or range of results. Examples of acceptance criteria for Performance Qualification involve sterility and temperature. For example, if the“acceptable criteria” for the temperature range within the chamber during sterilization is -0/ 3 Crelative to the actual set point, then the chamber temperature at all measured points must bewithin that range for a successful outcome to be recorded.How to Validate an Autoclave18

4. Result RecordThe Result Record is where all of the test data is recorded. At least three iterations are typically runfor process tests. Any failure to comply with the acceptance criteria makes an “iteration” a failedtest. The required number of iterations must be run successively with successful outcomes for thetest to be considered a pass. The record must include:Sterilizer cycle tape or electronic recordBiological (and chemical, if used) indicator resultsDatalogger results and their compliance with the Acceptance CriteriaAnalysis of the datalogger (thermocouple) records for accumulated lethality (Fo)and compliance with allowable load temperature ranges in the exposure phase5. VerificationAfter the testing is done, the results are typically reviewed for compliance with the acceptancecriteria. The review is finalized in this section with signatures from the person who ran the test and,preferably, with countersignature of a second person or manager.Sterility Testing & Record KeepingSterilization cycles are to be run sequentially and the load setup should follow the Procedure orSetup section of the test. Indicators and data logger probes are to be placed as specified. Sterilebarrier or closure materials are to be applied as specified. If sample loads are to be reused, theyshould be allowed to cool to a specified temperature (optimally room temperature) between cyclesto provide a real-world thermal load for the sterilizer and a real-world exposure for the indicators.In all tests, record keeping is essential to the integrity of the test. Records may include cycle tapeprintout from the sterilizer, data logger data files, photos, sketched diagrams, etc. These mustbe attached or provided with the report, with each identified by the section of the PQ protocol towhich it applies. Any electronic data records should be provided in a non-volatile form with the finalreport, i.e., as a CDROM or DVDROM, or via cloud storage.How to Validate an Autoclave19

A more extensive list of the required records is listed here:A catalog of who carried out the testing, the verification of results, and approvalswith initials and signaturesA listing of reference or other test equipment, manufacturer, model, serial number,and calibration due date, if applicableA listing of biological indicators and chemical indicators (if used), including manufacturermodel number, lot number, D-value, and nominal populationIf inoculum is used, a recovery study shall be done to ascertain the actual recoverablepopulation of the indicators; also, a growth promotion study shall be done to ensure thatthe item upon which the inoculum is deposited does not have a negative effect on outgrowth of the indicator organismA calibration record for test equipment (e.g. thermocouples) if done at the work-site,both before and after a series of tests and/or after the entire test protocol is performedA well-executed PQ will enable you to demonstrate and document thatthe autoclave can execute the desired processes and provide the sterilityassurance level that is required for your application.PQ is generally the final step in qualification. This testing creates an unassailable baselinelevel of proof of the autoclave’s ability to do the specified job, and is the basis forrequalification at periodic intervals.How to Validate an Autoclave20

6. Steam Quality TestingThe quality of the steam feeding an autoclave is an important factor in steam sterilization. Like time, temperature, and pressure, steam is a critical variable in the success andrepeatability of the sterilization process. As such, steam quality should be part of thevalidation of any steam sterilizer.How to Validate an Autoclave21

Steam quality is defined as the measurable physical aspects of steam used for sterilization. Thesephysical aspects include temperature (superheat), dryness (liquid water content), and non-condensable gas content. (Steam quality is not a measure of the impurity content of the steam.) Deviationsfrom established ranges of these aspects of the steam can result in the following issues:Wet loadsDamaged loadsUnsterile loadsSterilization (biological and chemical) indicator failuresStaining and corrosion of instruments and containersEach of these issues has a specific cause or causes and can usually be remedied.What to Know About Steam QualityAlmost every sterilizer manufacturer recommends “97% pure steam”. In general, this is notdefined, rarely measured, and, if discussed at all, is relegated to the mythology of sterilizer arcana.The good news is that essentially all laboratory autoclaves on the market today can provide sterile,dry, and intact sterilization loads if provided good quality steam from the steam supply. The badnews is that any autoclave can experience the above problems, and the cause is not always something that can be predicted.With careful design, following well-established principles, and proper maintenance, the system(steam supply and sterilizer) can be engineered to provide a large margin of security against steamquality noncompliance. For a production or GMP environment, steam quality testing should be partof annual preventative maintenance and qualification testing.When steam quality testing is performed, three parameters are measured:Steam DrynessThe amount of the steam by weight that is steam and notliquid waterNon-condensable gasesThe amount of the steam by volume that is not steamor water, but is air or other gas that does not contributemeaningfully to sterility of the loadSuperheatThe temperature of the steam above the temperature ofsaturated steam for a given moisture contentHow to Validate an Autoclave22

EN 285, the European Large Steam Sterilizer standard [1], is the world’s baseline authority forsteam quality acceptance criteria. It is referenced in most national standards and in ISO 17665 [2].With the release of EN 285:2015, the bar has been raised. The acceptance criteria are shown in thefollowing table.Steam DrynessNon-condensable gasesSuperheat 0.95 w/w* 3.5% v/v 25K*For laboratory autoclaves, 0.90 w/w is considered acceptable.Steam DrynessSteam dryness is calculated by measuring the temperature change in a known amount of waterin relation to the mass of steam that is required to cause that temperature change. Ideally, thetemperature rise is exactly proportional to the amount of steam delivered to the water to heat it,resulting in a dryness value of 1.0 (i.e. perfectly dry steam with no liquid water content.) Normally,the dryness value is less than 1.0, as there are thermal losses in any piping system even if it is wellinsulated. Because the dryness value of the steam at the chamber entry point can be quite a bitlower than the dryness value in the sterilizer, measurements of steam dryness should be made atboth locations.The acceptance criterion for steam dryness (the fraction of steam relative to water – 1.0 allsteam, no water) is at least 0.95, or 95% by weight. A dryness level down to 90% is consideredacceptable for laboratory autoclaves, however, steam below this value is considered to be wetsteam.Wet steam does not deliver as muc

been built and installed to speciication, and that all supporting services (i.e., utilities such as electricity, water, and steam) are available and connected properly. The IQ process methodically documents all aspects of the installation, the machine components, and any testing equipment used to provide a complete, closed-loop assessment.File Size: 1MBPage Count: 34Explore furtherAutoclave Validation FDA MHRA WHO EU GMP FLCVwww.validation-online.netAutoclave Sterilization Principle & Working PDF PPT .pharmawiki.inAutoclaves Qualification & Validationgmpua.comAutoclaving Guidelines for Sterilization of . - Lab Managerwww.labmanager.comAutoclave Log Sheet Word Doc Template [ Tracking Guide]consteril.comRecommended to you b