Spore Test Frequency After a Major Sterilizer Repair and in Daily Practice: RCDSO, BC, CDC, AAMI ST79 and CSA Z314

The short answer

There is no single "correct" spore test frequency, because the answer belongs to a jurisdiction, not to a product. In Ontario, a BI must be used to test the sterilizer each day that it is used and for each type of cycle that is used. In British Columbia, the published requirement is at least once a week for each sterilizer. The CDC and ANSI/AAMI ST79 use the same construction — at least weekly, but preferably every day that the sterilizer is in use — while Alberta, Saskatchewan and Nova Scotia guidance all describe daily in-office testing with a process challenge device. After a major repair or a failed cycle, the sources converge on a different number: three consecutive cycles, each challenged with a BI, before the sterilizer returns to service.

The rest of this page gives the exact wording, the document behind each number, and the four questions clinics ask when writing their own policy: routine frequency, what changes after a repair, what to do about a positive test, and what to record and keep.

How often does a sterilizer need a biological indicator?

Jurisdiction or standard	Document	Routine BI frequency	Where the BI goes
Ontario	RCDSO Infection Prevention and Control in the Dental Office (Standard of Practice, v3), p. 24; Public Health Ontario PIDAC guidance (3rd ed., 2013), p. 41	Each day that the sterilizer is used and for each type of cycle that is used	Inside a process challenge device (PCD)
British Columbia	BCCOHP / Oral Health BC Infection Prevention and Control Guidelines, Part C	At least once a week for each sterilizer used	Follow the manufacturer's placement directions
Alberta	Alberta infection prevention and control guidelines for oral health care (2024), adapted from Public Health Ontario	Each day a sterilizer is used and with each type of cycle	Inside a PCD, per the monitoring table
Saskatchewan	CDSS standard of practice IPC-04-04 (revised December 2022)	In-office BI every day for each sterilizer in a PCD, one control BI incubated each day, plus a weekly mail-in BI per sterilizer	Inside a PCD
Nova Scotia	NSRDHDTD IPAC Standards (May 2025)	In-office BI completed daily for each sterilizer using a PCD, plus a daily control BI	Inside a PCD
United States	CDC Guideline for Disinfection and Sterilization in Healthcare Facilities (2008, updated June 2024), p. 77 and p. 93	At least weekly (Category IB), with daily testing when the sterilizer is used frequently	In an appropriate test package or PCD
ANSI/AAMI ST79:2017	Section 13.5.3.2, Using biological indicators	At least weekly, but preferably every day that the sterilizer is in use	Inside a PCD
CSA Z314.3	Effective Sterilization in Health Care Facilities by the Steam Process (CAN/CSA-Z314.3)	The standard is sold commercially, so this table cites the public attribution rather than the clause text: Public Health Ontario attaches its biological monitoring requirements and its re-qualification requirements (clauses 12.4.3.2 to 12.4.3.4) to Z314.3	PCD preparation is addressed in Z314.3 clause 12.12, per the same provincial document

Two conventions matter when you read this table. First, "each type of cycle" is not decoration: a wrapped 134 °C cycle and an unwrapped cycle are separate monitoring obligations in Ontario, Alberta, Saskatchewan and Nova Scotia. Second, a weekly external mail-in test does not replace a daily in-office test where a daily requirement exists — in Saskatchewan, both are required, and they serve different purposes.

Ontario is daily, not weekly

Ontario clinics are the ones most likely to be told the wrong number. The regulator's own wording is unambiguous. Page 24 of the RCDSO standard states: "A BI must be placed in a PCD and used to test the sterilizer each day that it is used AND for each type of cycle that is used."

That text sits in a page whose bullet list is the RCDSO's own monitoring requirements, and the same page states that this section of the standard "meets or exceeds the recommendations of the PIDAC and the Canadian Standards Association (CSA)". Public Health Ontario's provincial guidance says the same thing in its own words on p. 41: "A biological indicator shall be used to test the sterilizer each day that it is used and with each type of cycle that is used that day."

To state it plainly: for an Ontario dental office, a weekly spore test schedule does not meet the provincial requirement. A weekly BI is the United States CDC and AAMI ST79 baseline, and it is also the British Columbia requirement. It is not the Ontario requirement.

What changes after a major repair, a relocation, or a failed cycle

The "after a repair" question has a sharper answer than the routine question, because both American and Canadian sources set a specific number.

Source	What is required after major repair, relocation, or process failure
CDC guideline (US), p. 74	All steam, ethylene oxide and other low-temperature sterilizers are tested with biological and chemical indicators on installation, on relocation, on redesign, after major repair, and after a sterilization failure. Three consecutive empty steam cycles are run with a BI and a CI in an appropriate test package or tray, and this is done for each type of steam cycle used.
ANSI/AAMI ST79:2017, §13.8.1	Qualification testing with a BI PCD is performed on all sterilizers after installation, relocation, malfunctions, major repairs, sterilization process failures, or changes to the utilities. Every cycle type in use is tested. For gravity-displacement sterilizers, three consecutive cycles are run with a PCD; dynamic-air-removal sterilizers are also tested with a Bowie-Dick pack.
Public Health Ontario PIDAC guidance, p. 37	Sterilizers must be monitored with a test load and fully re-qualified after major repairs, after construction, relocation or environmental change in the area, after unexplained sterility failures, and after changes in steam supply or delivery. A sterilizer is not approved for use if any BI yields a positive result.
RCDSO standard, p. 25	If a repeat BI is positive, or the cause of the original failure is not identified, the sterilizer stays out of service until it has been inspected, repaired and successfully re-challenged with BI tests in three consecutive cycles.
British Columbia IPAC Guidelines, Part C	A repaired sterilizer is re-challenged with BI tests in three consecutive empty chamber sterilization cycles before it returns to service.
Saskatchewan CDSS, IPC-04-04	Biological monitoring is completed when introducing a new sterilizer, following sterilizer repairs, and when introducing new packaging material; a repaired sterilizer is re-challenged with a BI in three consecutive empty chamber cycles.
Nova Scotia IPAC Standards, May 2025	Biological monitoring is completed following sterilizer repairs; a sterilizer that fails a repeat test remains out of service until re-challenged with a BI in three consecutive empty chamber cycles.

"Major repair" needs a definition, and ANSI/AAMI ST79 supplies one in §13.2: a repair outside the scope of routine preventive maintenance that significantly affects the performance of the equipment. The standard's examples include a software upgrade, or replacement of the water pump, detergent delivery system, heating system, water delivery system, water treatment system, ultrasonic generators, or computer controls. A door gasket change is routine maintenance. A control board replacement is not.

One practical note that clinics miss: the BI is not the only test after a repair. RCDSO requires that the preventive maintenance, servicing and repair of all reprocessing equipment be documented, and PIDAC's re-qualification list pairs the biological challenge with a full test load.

What happens when a spore test is positive

Every Canadian source reviewed for this page follows the same first three steps, in the same order: remove the sterilizer from service, review monitoring records back to the last negative BI, and determine whether operator error rather than mechanical failure explains the result. The RCDSO's own guidance is explicit that operator error is the most common cause of a positive BI: "In the event of a positive BI, it must be assumed that the cycle load was not sterilized, and that the sterilizer has malfunctioned, until a full investigation has proven otherwise."

Where the sources differ is in what happens to the load:

• RCDSO (p. 25): if the cause is identified, correct it, repeat the BI immediately using the same cycle, and keep the sterilizer out of service while awaiting the result. If the repeat is negative and the indicators are adequate, the sterilizer returns to service.
• CDC, Table 12 (p. 124): repeat the BI in three consecutive sterilizer cycles. Objects other than implants do not need to be recalled after a single positive test unless the sterilizer or the procedure is defective. If repeat tests stay positive, items processed since the last negative BI are considered nonsterile and are recalled and reprocessed.
• Alberta Health Services provincial SOP: if a second BI is positive, recall that load and every load back to the last negative BI, remove the sterilizer from service, reprocess recalled items in another sterilizer, and file a recall report recording the date, the circumstances, the corrective action, and the number of items to be recalled and actually recalled.
• British Columbia, Saskatchewan and Nova Scotia: recall items from suspect loads back to the last negative BI where possible and reprocess them. Nova Scotia adds that if instruments were used on patients after the last negative test, public health is contacted for direction.

Three data points explain why regulators put the emphasis on the process rather than the paperwork. Assessments of sterilizers in dental offices have found between 15% and 65% positive spore test results, and in one Minnesota study operator error rather than mechanical malfunction caused 87% of sterilization failures (CDC guideline, p. 21). After Alberta made daily BI testing mandatory for general dental practice, a 2021 JCDA study of 230 practices and 498 sterilizers reported 98% daily compliance, a 76-fold rise in annual testing volume, and an in-office positive rate of 0.034% against 0.52% for external mail-in testing. A 2024 BMC Oral Health study of 198,771 indicators from 362 Saskatchewan clinics (2015–2022) found a 0.20% failure rate, improving from 0.51% to 0.15%, with 91.8% of failures traced to human factors.

Records: what to write down and how long to keep it

Jurisdiction or standard	What must be recorded	Retention period
Ontario (RCDSO standard, p. 25)	Daily operation of every sterilizer, including any malfunction and the action taken, in a dedicated log book	At least 10 years from the date of the last entry
Nova Scotia (IPAC Standards, May 2025)	Daily in-house biological monitoring records showing the sterilizer, date, time and the signature of the staff member	Recommended 3 years
Saskatchewan (CDSS IPC-04-04)	Date, sterilizer and cycle number for each BI, signed; daily records of in-house monitoring	No period stated in the public standard
British Columbia and Alberta	Daily review and documentation of sterilizer operation; results of physical, chemical and biological monitoring recorded per load	No period stated in the public guideline
CDC guideline, p. 80	Results of physical, chemical and biological monitoring	Per accreditation and state or federal rules; the CDC notes that one accreditation body asks for 3 years
ANSI/AAMI ST79:2017, §13.3.4	Sterilization monitoring records	No fixed period: retained according to facility policy, which the standard says should be based on local, state, federal and accrediting agency requirements

The gap between 3 years and 10 years is the single easiest compliance failure to prevent, because it costs nothing to keep a log book longer than the minimum. If a clinic works across provinces, or is part of a group with practices in more than one province, the longest applicable retention period is the safe default.

Why you will still see "weekly" quoted for Canada

Weekly is not a myth, it is a jurisdiction. The CDC's 2008 guideline, still current after its June 2024 update, recommends at least weekly monitoring and says daily testing is preferable when a sterilizer is used frequently; AAMI ST79:2017 uses the same construction in §13.5.3.2; British Columbia's published guideline applies a weekly minimum. Pages that quote a weekly frequency as a general Canadian or Ontario number are usually repeating an American baseline, or a provincial one with the province left off.

Two habits prevent that confusion. Cite the document rather than the frequency — "daily, per RCDSO Standard of Practice v3, p. 24" is checkable, "weekly is standard" is not — and record the retrieval date, because these documents are revised. The RCDSO standard reviewed here is version 3, the BCCOHP guidelines date from 2022, and the CDC document carries a June 2024 update notice.

How this table was built

Every frequency on this page was read directly from the document named beside it: the RCDSO IPAC standard (PDF, v3), the Public Health Ontario PIDAC provincial guidance (3rd edition), the CDC disinfection and sterilization guideline (2008 text with the June 2024 update), ANSI/AAMI ST79:2017, the Alberta Health Services positive-BI procedure, the BCCOHP / Oral Health BC guidelines, Saskatchewan's CDSS standard IPC-04-04, and the Nova Scotia IPAC standards.

Two limits are stated openly. CSA Z314.3 is a commercial standard whose clause text is not public, so references to it here follow how Public Health Ontario cites it rather than quoting the standard. And four provinces — Quebec, New Brunswick, Newfoundland and Labrador, and Prince Edward Island — had no dental-specific BI frequency in a public document at the time of writing. That is not the same as having no requirement: those standards may be distributed to registrants only, and the clinic's own written policy is what an inspector will ask for. No frequency was inferred from a neighbouring province.

Where the test kits fit

Everything above stands on its own: these are regulators' requirements, and a clinic can meet them with any product that fits its sterilizer and cycle. For a clinic setting up daily testing for the first time the practical constraints are the read time and the incubator, not the indicator: a 24-hour readout indicator, a dry-block incubator validated to hold 57-60 °C, and a log book with a column per cycle type cover most of what the documents above ask for. The RCDSO's list of operator errors — overloading, poor package separation, excessive packaging and incorrect PCD placement — is a useful checklist to keep beside the sterilizer. Clinics that want to test the reading step before committing to a format can use the 5-pack biological indicator trial that CliniEco Medical ships in Canada: it is a sample, not a subscription, and nothing in the tables above depends on it.

Related reading

Ontario's daily requirement sits inside a larger comparison of the two standards most often cited together: AAMI ST79 vs CSA Z314, compared line by line. If you work across provincial lines, Ontario and British Columbia, side by side sets the two schedules against each other. And when a test does come back positive, the step-by-step investigation protocol walks through the first hours.

Frequently Asked Questions

How often do you need a spore test in an Ontario dental office?

Every day the sterilizer is used, and for each type of cycle used that day. The RCDSO standard states that a biological indicator must be placed in a process challenge device and used to test the sterilizer each day that it is used and for each type of cycle that is used. Public Health Ontario's provincial guidance uses the same wording.

Is a weekly spore test ever acceptable?

Yes, in some jurisdictions. British Columbia requires biological indicators at least once a week for each sterilizer used, and the CDC and AAMI ST79 baseline is at least weekly with daily testing preferred for frequently used sterilizers. A weekly schedule does not meet the Ontario requirement, which is daily per cycle type.

How many biological indicators are needed after a major sterilizer repair?

Three, in consecutive cycles. The CDC guideline calls for three consecutive empty steam cycles run with a biological and chemical indicator in a test package for each type of steam cycle used. AAMI ST79 section 13.8.1 requires qualification testing with a BI process challenge device after major repairs, with three consecutive cycles for gravity-displacement sterilizers. The RCDSO, BC, Saskatchewan and Nova Scotia documents all describe re-challenging a repaired sterilizer with BI tests in three consecutive cycles.

What counts as a major repair to a sterilizer?

AAMI ST79 section 13.2 defines it as a repair outside the scope of routine preventive maintenance that significantly affects the performance of the equipment, and gives examples such as a software upgrade or replacement of the water pump, heating system, water delivery system, water treatment system, ultrasonic generators or computer controls. Routine preventive maintenance such as a gasket inspection is a different category.

How long must sterilization monitoring records be kept?

In Ontario, the sterilization log book must be maintained for at least 10 years from the date of the last entry. Nova Scotia recommends 3 years. AAMI ST79 does not set a fixed period and leaves retention to facility policy, which should be based on local, state, federal and accrediting requirements. Keeping records for the longest applicable period is the safe default.

Does every test need a control biological indicator?

Saskatchewan and Nova Scotia both require a control biological indicator to be incubated each day to confirm the incubator is functioning, in addition to the test indicator. ANSI/AAMI ST79 describes a positive control as a BI from the same lot left unexposed to the cycle and incubated to verify the viability of the test indicator. When a control from the same lot fails to grow, the test results are considered invalid.

What should happen when a spore test is positive?

Remove the sterilizer from service, review all monitoring records back to the last negative biological indicator, and determine whether operator error rather than mechanical failure caused the result. Repeat the test immediately using the same cycle. If the repeat is negative and the physical and chemical indicators are adequate, the sterilizer returns to service. If the repeat is positive or no cause is identified, the sterilizer stays out of service until it is inspected, repaired and re-challenged with three consecutive biological indicator cycles, and items from suspect loads back to the last negative test are recalled where possible.

Does the biological indicator have to go inside a process challenge device?

In Ontario, Alberta, Saskatchewan and Nova Scotia the requirement is written as a BI in a process challenge device, and AAMI ST79 section 13.5.3.2 requires BIs to be used within process challenge devices for routine monitoring. British Columbia requires that the manufacturer's placement directions be followed and requires a BI for every load containing implantable devices.

CliniEco Medical supplies biological indicators, process challenge devices, incubators and readers to Canadian dental, long-term care, veterinary, food and industrial facilities. MDEL #35334. Customer service: +1 (437) 466-2232.

Sources

• RCDSO, Infection Prevention and Control in the Dental Office, Standard of Practice v3 (PDF)
• RCDSO, Potential Causes of a Positive Biological Indicator (PDF, revised 02/24)
• Public Health Ontario, PIDAC provincial guidance on cleaning, disinfection and sterilization in all health care settings (PDF, 3rd ed. 2013)
• CDC, Guideline for Disinfection and Sterilization in Healthcare Facilities (PDF, 2008 text, updated June 2024)
• BCCOHP / Oral Health BC, Infection Prevention and Control Guidelines (PDF)
• Alberta infection prevention and control guidelines for oral health care, 2024 (PDF)
• Saskatchewan CDSS, standard of practice IPC-04-04, Monitoring Sterilization (PDF, revised December 2022)
• Nova Scotia NSRDHDTD, IPAC Standards for oral health care (PDF, May 2025)
• Alberta Health Services, Management of Positive Biological Indicator or Failed Sterilization Mode (PDF SOP)
• ANSI/AAMI ST79:2017, Comprehensive guide to steam sterilization and sterility assurance in health care facilities (standard page)
• Kunyk et al., Daily Use of Biologic Indicators in General Dental Practice, JCDA 2021 (PDF)
• Vatanparast et al., Retrospective study of external biological indicator testing in Saskatchewan dental clinics, BMC Oral Health 2024
• Sterilization monitoring collection — CliniEco Medical
• Biological indicators explained: the gold standard of sterilization monitoring
• Sterilization compliance hub — CliniEco Medical
• 5-pack biological indicator trial — CliniEco Medical