How do I know if my autoclave is working properly?
Monday, 8:40 in the morning. The autoclave finishes a cycle, the printout shows 134 °C for the programmed hold time, and the packs go onto the shelf. Ten days later someone asks how the clinic knew that load was safe to use, and the printout turns out to answer a narrower question than most teams assume: it proves the chamber reached the values the machine was set to reach.
A sterilizer can be faulty in ways the printout cannot see. A door gasket that is starting to leak lets air back into the chamber. A filter that has not been changed cuts steam quality. A tray packed too tightly blocks penetration. A pouch whose paper side stayed damp through the dry phase wicks moisture back in. Each of those can produce a cycle that looks correct on paper and a load that is not sterile, which is why monitoring is built in layers rather than around one number.
The biological layer is the only one that answers "did this cycle kill things". Culture-based readouts take up to 48 hours, so clinics often treat it as paperwork that runs behind the real work. A 20-minute rapid-readout biological indicator compresses that wait to roughly the length of a coffee break, which changes the practical question from "when will we know" to "what do we do while we wait".
What three checks does a working autoclave pass on the same day?
Ontario's dental standard requires monitoring through a combination of physical, chemical and biological means, and requires written policies and procedures for it (RCDSO, Infection Prevention and Control in the Dental Office, Monitoring of sterilization, p.22). The three arms answer different questions, and none of them substitutes for another.
| Check | What it confirms | What it cannot confirm |
|---|---|---|
| Physical parameters | The chamber reached the set time, temperature and pressure | That steam reached the inside of the package |
| Type 1 external indicator | The package was exposed to a sterilization process | That conditions inside the package were adequate |
| Type 4, 5 or 6 internal indicator | The conditions inside that package met the values the indicator is built to respond to | That a resistant spore population was killed |
| Type 2 Bowie-Dick test | Air removal worked in an empty chamber at the start of the day | That later loads were penetrated or released correctly |
| Biological indicator | Spores in that cycle type were killed | That instruments were clean on the way in |
The internal indicator rules are tighter than most loading benches assume. RCDSO requires a Type 1 indicator on the outside of every package and a Type 4, Type 5 or Type 6 chemical indicator inside it (p.23). Public Health Ontario puts the boundary plainly: chemical indicators do not replace the need to use a biological indicator (Cleaning, disinfection and sterilization guidance (PIDAC 2013), p.38). The classes themselves come from ISO 11140-1, which sorts chemical indicators from Type 1 through Type 6 by which process variables each one responds to. The consumables that carry those classes sit in one place in the catalogue, which is convenient when a clinic is restocking rather than researching: autoclave monitoring consumables.
How often must each check run in Canada?
Frequency is where Canadian practice and American supplier literature part ways most often.
- Every load: physical parameters checked and documented. With a recording device, at the conclusion of the cycle for each load; without one, during the cycle (RCDSO, p.22).
- At the start of each day the sterilizer is used: an air removal test with a Type 2 indicator on pre-vacuum sterilizers, process challenge device in an empty chamber (RCDSO, p.23). A Bowie-Dick test pack built for that daily check is sized so the pack itself does not become the variable.
- Every day the sterilizer is used, and with every cycle type used that day: a biological indicator (PHO, p.40). The second half of that sentence is the part clinics miss. A gravity cycle in the morning and a pre-vacuum cycle in the afternoon are two tests, not one.
- Every package: an external Type 1 indicator plus an internal Type 4, 5 or 6 (RCDSO, p.23).
Weekly spore testing is a real baseline in the United States and it shows up in a great deal of brochure copy north of the border. It is not the Ontario position, and a clinic that runs a weekly programme while telling an auditor it follows RCDSO has a documentation problem that has nothing to do with the sterilizer.
What does a passing indicator actually prove?
A tape that turns dark means the package saw heat. A Type 5 or Type 6 dot that passes means the conditions inside that package met a stated performance value, which is why those classes can support a documented release decision. Neither is a sterility claim. RCDSO states that physical and chemical indicators do not ensure that sterilization has been achieved; they verify that the necessary conditions were met, and if either shows inadequate reprocessing the items must be reprocessed (p.23).
That distinction changes how the bench talks. "The tape went dark, so it is sterile" is not a defensible sentence in an audit, and it is not a defensible sentence to a patient. What the tape supports is narrower and still useful: this package was processed, and this package's internal conditions were in range.
How do I catch a failing sterilizer before a patient is treated?
Load release is the control point. RCDSO requires that loads containing implantable devices be quarantined until the biological indicator result is known, and that routine loads not be released before the result is available unless a Type 5 or Type 6 chemical indicator plus the specific cycle physical parameters justify release (p.23).
Two workable setups exist. Clinics with a small incubator run a 24-hour biological indicator in a dry-block incubator on the reprocessing bench and read it the next morning, holding the previous day's load in a marked tray. Clinics with rapid readout technology do the same thing inside a single shift, which keeps quarantine short enough that it does not collide with the day list.
When a biological indicator comes back positive, the sequence is fixed: remove the sterilizer from service, review the physical and chemical records since the last negative result, retest immediately using the same cycle that failed, and keep the unit out of service until the repeat is negative and indicators are adequate (RCDSO, p.24). Operator error accounts for a large share of these events, usually overloading, poor package separation, or packaging that is too dense for the cycle.
Which records show the sterilizer was working?
The daily operation of every sterilizer must be reviewed and documented in a log book, any malfunction noted, and the log kept for at least 10 years from the date of the last entry (RCDSO, p.24). Ten years is the number that decides the format. A paper book that walks off with a retiring office manager is a ten-year liability.
Labels carry the other half of the evidence: date reprocessed, sterilizer used, cycle or load number, and the initials of the person who ran it, applied without puncturing or dampening the package (RCDSO, p.21). Audits work backwards from a package on the shelf to the label, and from the label to the log entry. Where the two disagree, the record reads as reconstructed rather than contemporaneous.
What if the sterilizer has no recording device?
Then the indicator burden moves inside the package. A Type 5 or Type 6 chemical indicator must be placed in each package to be released, and the physical parameters must be checked during the cycle for every load (RCDSO, p.24). RCDSO is direct that recording devices are preferred, and that all new sterilizers must have the feature (p.22). A clinic buying equipment should treat the printout, or the electronic cycle record, as part of the monitoring system rather than an accessory.
None of this requires a compliance department. It requires three measurements on the same day, one log that survives a decade, and a release rule that holds when the schedule is running late. The clinics that get into trouble are rarely the ones with a broken sterilizer; they are the ones with no way to show, after the fact, that it was working.
References
- Infection Prevention and Control in the Dental Office — Standard of Practice (RCDSO) (checked 29 October 2026)
- Cleaning, disinfection and sterilization of medical equipment and devices in all health care settings (Public Health Ontario) (checked 29 October 2026)
- Reprocessing (Public Health Ontario) (checked 29 October 2026)
- ISO 11138-1:2017 Sterilization of health care products — Biological indicators — General requirements (checked 29 October 2026)
- ISO 11140-1:2014 Sterilization of health care products — Chemical indicators — General requirements (checked 29 October 2026)
Printable companion: the free sterilization log sheet lists every field the three checks below produce, so the record gets written as the work happens instead of being rebuilt before an inspection.
Testing a sterilizer you have not run before? The sterilization self-check walks through the same questions in about ten minutes and prints a record you can file.
Not sure how this applies to your own setup? Ask a sterilization compliance specialist — you’ll get a written answer specific to your equipment and province, with the regulation or standard cited.
Reselling or buying for a facility? become a distributor for wholesale and multi-site ordering.
Related Reading
- Sterilization log requirements in Ontario: what auditors ask for
- Bowie-Dick test frequency in Canada and the US
- Biological indicators for autoclaves: spore testing protocols for Canadian clinics
Frequently Asked Questions
Does a colour change on the tape mean the load is sterile?
No. An external Type 1 indicator shows that the package went through a cycle; it cannot show that steam penetrated a wrapped cassette or that spores were killed. RCDSO states that physical and chemical indicators do not ensure sterilization has been achieved (Monitoring of sterilization, p.23). The biological indicator is the check that addresses killing, not exposure.
How often must a spore test run in an Ontario dental office?
Every day the sterilizer is used, and with each type of cycle used that day. That is the Public Health Ontario wording (PIDAC, p.40). A weekly spore test is the American baseline and it appears in a lot of supplier material, but it is not the Ontario position.
Do I need a Bowie-Dick test every day?
For pre-vacuum (dynamic air removal) sterilizers, yes: an air removal test must be performed at the beginning of each day that the sterilizer is used, with the process challenge device in an empty chamber (RCDSO, p.23; PHO, p.40). A gravity displacement unit does not take a Bowie-Dick test.
Can I release a load before the biological indicator reads?
Public Health Ontario allows release of routine loads before the result if a Class 5 or 6 chemical indicator and the cycle's physical parameters justify it (p.40). Loads containing implantable devices must be quarantined until the result is known (RCDSO, p.23).
How long does the sterilization log have to be kept?
At least 10 years from the date of the last entry in that record, not from the date of the cycle (RCDSO, p.24). That single sentence usually decides whether the log lives on paper or in software.
What if the sterilizer has no recording device?
A Type 5 or Type 6 chemical indicator must go inside every package to be released, and the physical parameters must be checked during the cycle for each load (RCDSO, p.24). RCDSO also states that tabletop sterilizers with recording devices are preferred and that all new sterilizers must have this feature (p.22).
Last updated: October 2026. CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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