Study by domain
The Sterilization Process
Twenty one percent of the exam and the densest domain for numbers: cycle parameters, air removal testing, biological monitoring, and the low temperature methods.
The short answer
Sterilization Process is 21% of the CRCST exam. Recognized minimum exposure is 30 minutes at 121 C in a gravity displacement sterilizer or 4 minutes at 132 C in a prevacuum sterilizer. Air removal is verified daily with a Bowie-Dick test in an empty chamber, and lethality is monitored with biological indicators.
| Domain, as the outline names it | Sterilization Process |
|---|---|
| Share of the exam | 21% |
| Questions on a 150 question paper | about 32 |
What you need to know
Each point below carries the sentence from the public standard that supports it, with the date it was read. You are not being asked to take our word for any of it.
The four parameters of steam sterilization
Steam, pressure, temperature and time. Pressure is on the list for a specific reason the guideline spells out: it is the means of reaching the high temperatures that kill microorganisms quickly. Pressure itself is not what kills, it is what makes the temperature possible, and that distinction is a common exam target.
Autoclave temperature and time: gravity versus prevacuum
Thirty minutes at 121 C in a gravity displacement sterilizer, or four minutes at 132 C in a prevacuum one. The prevacuum cycle is dramatically shorter at a higher temperature because a vacuum pump removes the air before steam is admitted, giving nearly instantaneous penetration. In a gravity sterilizer the steam has to push the air out, and the residual air is what stretches the exposure period.
The Bowie-Dick test: when, and in what
Each day the vacuum type sterilizer is used, before the first processed load, in an otherwise empty chamber. The empty chamber is not a technicality: a load would give the steam somewhere to go and mask the very air leak the test exists to find. A uniform color change passes, and a spot means entrapped air.
Biological indicators and which spore goes with which process
Geobacillus stearothermophilus monitors steam, hydrogen peroxide gas plasma and peracetic acid. Bacillus atrophaeus monitors ethylene oxide and dry heat. The spore is chosen because it is unusually resistant to that specific process, so surviving spores mean the cycle failed. A useful anchor: the thermophile monitors the heat process, and it incubates at 55 to 60 C while B. atrophaeus incubates at 35 to 37 C.
Implant loads
Every load containing implantable objects is monitored biologically, not weekly like the rest, and where feasible the implants are not used until the spore test reads negative. Implants are the one category where a sterilization failure leaves a nonsterile device inside a patient, which is why the same section says objects other than implants do not need recall after a single positive spore test.
Immediate use and flash sterilization
Acceptable for cleaned items that cannot be packaged, sterilized and stored before use. The guideline rules out the three reasons it usually gets used by name: convenience, avoiding the purchase of another instrument set, and saving time. Note the word cleaned, too. Flash shortens the sterilization step and changes nothing about the cleaning that has to precede it.
Ethylene oxide: parameters and aeration
Four essential parameters, and they are not the same four as steam: gas concentration, temperature, relative humidity and exposure time. Humidity is on the list because water molecules carry the gas to the reactive sites. Aeration is part of the process rather than a courtesy, because the guideline records patient tissue burns caused by residual ethylene oxide in implants.
Reading is not the same as being ready
Knowing this domain and being able to answer questions on it under a clock are different skills, and the exam tests the second one. The free practice test is scored domain by domain, so it will tell you whether this one is actually costing you points or whether your problem is somewhere else.