Autoclave Spore Test Failed: Exactly What to Do Next

A failed biological indicator (BI) spore test is one of the most stressful events an office manager can face. Your first instinct might be panic — but the protocol is clear, manageable, and completely survivable if you follow the right steps immediately. Here's exactly what to do.

What a Failed Spore Test Actually Means

A biological indicator contains Geobacillus stearothermophilus spores — among the most heat-resistant organisms known. If those spores survive your autoclave cycle, the sterilizer did not reach the conditions needed to kill them. That means surgical instruments processed in that cycle cannot be considered sterile.

One failed test is not necessarily evidence of widespread instrument contamination — spore tests can fail due to operator error, a bad indicator strip, or a single malfunctioning cycle. But it is a signal that something is wrong and must be investigated.

Immediate Steps — Do This Today

1. Stop using the autoclave for patient instrument sterilization immediately. Label it "OUT OF SERVICE."
2. Quarantine all instrument loads processed since the last passing spore test. Do not use those instruments until you have a passing retest result or confirmed resolution.
3. Notify your dentist/owner before end of business day.
4. Contact your spore test service (mail-in lab or in-office incubator) to confirm the result was not a handling/incubation error.
5. Arrange backup sterilization if you have another autoclave. If not, contact a neighboring practice about temporary use, or use sterile single-use instruments only.
6. Call a certified dental equipment technician for same-day assessment — most causes of spore test failure are mechanical and fixable.

Documentation You Must Create

California and OSHA both require you to document the failure and your response. Create a written record that includes:

• Date and time the failed result was received
• Lot number and expiration date of the biological indicator
• Cycle type, temperature, time, and pressure settings used
• Names of all loads processed since last passing test
• Actions taken (quarantine, notification, service call)
• Date of retest and result
• Technician name, service performed, and date of repair (if applicable)

Why Spore Tests Fail: The Most Common Causes

Cause	Frequency	Fix Type
Overloaded or improperly packed pouches	Very common	Operator training
Instruments not fully dry before pouch sealing	Common	Process change
Faulty or expired spore test strip	Common (1st step)	Retest with new strips
Temperature not reaching 270°F / 132°C	Common	Tech repair — thermostat or heating element
Steam penetration failure (air pocket in chamber)	Moderate	Tech repair — door gasket or vacuum system
Short cycle time (timer malfunction)	Less common	Tech repair — control board
Low pressure (pressure relief valve stuck)	Less common	Tech repair — PRV replacement

Retest Protocol

Before retesting, run a complete empty-chamber cycle. Then:

1. Use a fresh, unexpired biological indicator from a new lot if possible
2. Place the BI in the most challenging location: center-back of the lower tray
3. Run your standard sterilization cycle (do not use a special "test" setting)
4. Incubate per manufacturer instructions (24 or 48 hours depending on method)
5. If the retest passes AND you've identified/corrected a process error, you can resume use — document everything
6. If the retest fails again, the problem is mechanical — do not use the autoclave until repaired and retested passing

When to Call for Repair

Call a dental equipment technician immediately if:

• Two consecutive spore tests fail
• You cannot identify a clear operator error that explains the failure
• The autoclave displays error codes, unusual sounds, or pressure fluctuations
• The chamber is not reaching target temperature (see our autoclave temperature guide)

We service all major autoclave brands in Ventura County and surrounding areas: Midmark M11/M9, Tuttnauer 2340/3870, Pelton & Crane Delta Q/Magnaclave, Scican Statim, and Dentsply Ritter. Same-day service available for practices in Oxnard, Ventura, Camarillo, Thousand Oaks, Simi Valley, Santa Barbara, and the San Fernando Valley.

California Dental Board Requirements

Under California Code of Regulations Title 16, Section 1005, dental practices must:

• Use biological monitoring (spore tests) at least weekly on each sterilizer
• Use a certified laboratory or a validated in-office incubation system
• Maintain records of all spore test results for inspection
• Not use an autoclave with a confirmed failed spore test until the malfunction is corrected and a passing result is achieved

Questions about your autoclave's compliance status? Call us at (424) 527-9914. We serve all Ventura County cities, Santa Barbara County, and the San Fernando Valley.