Laboratory sterilizers are critical for experimental safety, yet operators often fall into errors due to inexperience or negligence, leading to sterilization failure, equipment damage (such as pressure vessel explosions), or even safety accidents (such as burns). Below are five common misconceptions and their corrective measures.
Misconception 1: Overcrowding the load, obstructing steam circulation
Phenomenon: Tightly stacking items like Petri dishes and test tubes (spacing <1 cm), or even placing entire incubator trays directly into the sterilizer.
Consequences: Steam cannot penetrate the gaps between items (local temperatures may reach only 80–90°C), creating "cold spots" or sterilization dead zones (e.g., the actual temperature of items at the bottom is 10–15°C lower than those at the top).
Correction: Leave a 2–3 cm gap when loading (a thermometer should fit between items to verify spacing); leave liquid containers open (to prevent bursting); and place fabrics loosely. For example, Petri dishes should be placed upside down in a single layer, and test tubes should be separated using specialized sterilization racks.
Misconception 2: Neglecting the air-purging step, leaving residual cold air
Phenomenon: Immediately starting the sterilization cycle (without manually or automatically purging cold air from the chamber), assuming that "reaching the target temperature means sterilization is complete."
Consequences: Cold air occupies space (if it accounts for >10% of the volume, the actual sterilization temperature is 10–20°C lower than the displayed value; e.g., a display of 121°C might actually correspond to only 105–110°C). Correction: Autoclaves require an "exhaust" cycle to purge cold air (indicated by continuous steam venting from the exhaust port, or the pressure gauge needle rising, dropping to zero, and then rising again), while dry-heat sterilizers require preheating (for over 30 minutes) to ensure uniform internal air temperature.
Misconception 3: Incorrect parameter settings or improper matching
Observation: Using identical parameters (e.g., 121°C/20 minutes) for all items, without distinguishing between material types (e.g., liquids vs. instruments) or packaging (e.g., breathable vs. sealed).
Consequences: Liquids (such as culture media) require a longer cycle (30 minutes) to prevent explosive boiling, while sealed packages (such as plastic bags) require a higher temperature (134°C) to ensure steam penetration.
Correction: Adjust parameters based on item type—121°C/20 minutes for instruments, 121°C/30 minutes for liquids, and 134°C/10 minutes for heat-resistant metal; use standard parameters for breathable packaging, but extend the cycle by 10–15 minutes for sealed packaging.
Misconception 4: Forcing the door open before pressure returns to zero
Observation: Opening the sterilizer door after the cycle finishes without waiting for the pressure gauge needle to return to zero (or for the safety valve to close).
Consequences: If internal pressure exceeds 0.1 MPa, high-temperature steam (>120°C) can blast out instantly, causing severe burns to the face and hands (laboratories have experienced third-degree burn accidents due to this).
Correction: Allow the unit to cool naturally until the pressure reaches zero (approximately 30–60 minutes); if items must be retrieved urgently, use the slow exhaust mode (depressurization rate <0.05 MPa/minute) and wear heat-resistant gloves.
Misconception 5: Neglecting regular maintenance and operating faulty equipment
Observation: Failure to clean the sterilizer chamber (removing residual chemical deposits or limescale) or to calibrate the pressure gauge (deviation >±10 kPa) and temperature sensor (deviation >±3 °C) over long periods.
Consequences: Limescale buildup can clog pipelines (impeding steam circulation), while sensor errors can result in insufficient actual temperatures (leading to sterilization failure). Corrective measures: Clean the inner chamber weekly (wipe with a soft cloth; do not use steel wool); inspect the safety valve monthly (manually lift it to test for smooth operation); and calibrate the pressure gauge and temperature sensor quarterly (compare against standard instruments).
By avoiding these pitfalls, laboratory sterilizers can truly serve as tools for ensuring sterility rather than becoming sources of safety hazards. Standardized operation and regular maintenance demonstrate a fundamental respect for both experimental results and personal safety.