Procedure for Operation and Calibration of Lab Oven

1.0 Purpose:

  To lay down the Procedure for Operation and Calibration of Lab Oven.

2.0  Scope: 

This procedure applies to operation and calibration of lab oven used for sterilization of lab accessories.

3.0       Responsibility:      

3.1       The responsibility of operation and calibration of lab oven lies with Microbiologist/Analyst.

4.0       Definitions/Abbreviations: Nil

5.0       Procedure:

5.1       Operating Procedure of Lab Oven:

5.1.1    The lab oven is used for sterilization of sampling flasks, glassware and instruments (scissors, spatulas, and forceps etc.) at 181º C for 2 hours.

5.1.2    Arrange petri plates in closed SS trays, instruments (pipette, scissors and forceps) in SS  pipette jar. Keep pipette jars and sampling containers in the rack.

5.1.3Switch ‘ON’ the main switch.

5.1.4Switch on the ‘Main’ switch located at the top right hand side of the lab oven. The display should show the inside temperature and chamber fan should be on.

5.1.5Set the temperature 181 °C by pressing ‘Up’ and ‘Down’ keys on the control panel. The bottom display will show the set temperature and the top display will show the actual temperature.

5.1.6Set the safety knob to 5°C above the set temperature on the temperature control. The safety thermostat will cut off the heat supply in case of overshoot of temperature.

5.1.7Check that ventilator at the right hand side of the chamber is partly open.

5.1.8Run the sterilization cycle at 181± 2 °C for 2 hours.

5.1.9Record the load details and temperature in the format, xxxxx.

5.1.10After completion of sterilization switch off the ‘Main’ switch and leave it for cooling.

5.2       Calibration of Lab Oven:

5.2.1    The procedure for the operation of lab oven shall be carried out as per ‘Procedure of operation of lab oven.

5.2.2The calibration of the lab oven shall be carried out for Empty chamber, Minimum load and Maximum load.

5.2.3Record details of the materials and equipments used in the calibration of the lab oven in the form xxxxx.

5.2.4    Calibration of Lab Oven with  Empty Chamber:

5.2.4.1Arrange the 10 biological indicators (Bacillus subtilis spore strips) each kept in one pertriplate in the empty chamber of the oven systematically at different locations of the lab oven as shown in annexure-1.

5.2.4.2Close the door tightly and set the temperature to 181º C on the control panel of the oven and set the safety knob to 5º C above the set temperature.

5.2.4.3Check that ventilator at the right hand side of the chamber is closed.

5.2.4.4The sterilization cycle shall be run at 181º± 2ºC for 2 hours.

5.2.4.5Record the display temperature for every 15mins in the observation report format, xxxxx.

5.2.4.6After completion of the sterilization cycle switch off the ‘Main’ switch and leave it for cooling. After cooling collect all the spore strips from lab oven.

5.2.4.7The sterility of the spore strips shall be tested by direct inoculation method.

5.2.4.8Inoculate the each spore strips in 30ml of sterile soyabean casein digest broth medium tubes in front of LAF bench. Ensure that the spore strips should immerse in the medium.

5.2.4.9Positive and Negative controls shall be run along with test samples. For positive control inoculate spore strips (without sterilization cycle) in 30ml of sterile soyabean casein digest broth medium tubes.  For negative control incubate 30ml of sterile soyabean casein digest broth medium tube without inoculating the spore strip.

5.2.4.10Incubate all the tubes at 30-35 º C for 7 days.

5.2.4.11Observe the each inoculated medium every day and record the results in the Test report format, xxxxx.

5.2.4.12If positive control shows early and copious growth remove the tube.

5.2.4.13Negative control should not show growth up to 7 days.

5.2.5    Calibration of Lab Oven with Minimum Load:

5.2.5.1Place the 2 SS trays each contains 24 no’s of petriplates, 2 pipette jars and 10nos of biological indicators in the lab oven as per the annexure-2.

5.2.5.2Close the door tightly and set the temperature to 181ºC on the control panel of the oven and set the safety knob temperature to 5 º C above the set temperature.

5.2.5.3Check the ventilator at the right hand side of the chamber is closed.

5.2.5.4The sterilization cycle shall be run at 181º ± 2 º C for 2 hours.

5.2.5.5Record the display temperature for every 15mins in the observation report format, xxxxx.

5.2.5.6After completion of the sterilization cycle switch off the ‘Main’ switch and leave it for cooling. After cooling collect all the spore strips from the oven.

5.2.5.7Sterility of the spore strips shall be tested by direct inoculation method.

5.2.5.8Inoculate the each spore strips in 30ml of sterile soyabean casein digest broth medium tubes in front of LAF bench. Ensure that the spore strips should immerse in the medium.

5.2.5.9Positive and Negative controls shall run along with test samples. For positive control inoculate spore strips (without sterilization cycle) in 30ml of sterile soyabean casein digest broth medium tubes. For negative control incubate 30ml of sterile soyabean casein digest broth medium tube without inoculating the spore strips.

5.2.5.10Incubate all the tubes at 30-35 º C for 7 days.

5.2.5.11Observe the each inoculated medium every day and record the results in the test report Format, xxxxx.

5.2.5.12If positive control shows early and copious growth remove the tubes.

5.2.5.13Negative control should not show growth up to 7 days.

5.2.6    Calibration of Lab Oven with Maximum Load:

5.2.6.1Place the 5 SS trays with each 24 petriplates, 10nos of biological Indicators and 2nos of pipette jars in the oven as per annexure-3.

5.2.6.2Close the door tightly and set the temperature to 181º C on the control panel of the oven and set the safety knob temperature to 5º C above the set temperature.

5.2.6.3Check the ventilator at the right hand side of the chamber is closed.

5.2.6.4The sterilization cycle shall be run at 181º ± 2º C for 2 hours.

5.2.6.5Record the display temperature for every 15mins in the observation report format, xxxxx.

5.2.6.6After completion of the sterilization cycle switch off the ‘Main” switch and leave it for cooling. After cooling collect all the spore strips from lab oven.

5.2.6.7Sterility of the spore strips shall be tested by direct inoculation method.

5.2.6.8Inoculate the each spore strips in 30ml of sterile soyabean casein digest broth medium tubes in front of LAF bench. Ensure that the spore strips should immerse in the medium.

5.2.6.9Positive and Negative controls shall run along with test samples. For positive control inoculate spore strips (without sterilization cycle) in 30ml of sterile soyabean casein digest broth medium tubes. For negative control incubate 30ml of sterile soyabean casein digest broth medium tube without inoculating the spore strip.

5.2.6.10Incubate all the tubes at 30-35 º C for 7 days.

5.2.6.11Observe the each inoculated medium every day and record the results in the test report format,xxxxx.

5.2.6.12If positive control shows early and copious growth remove the tubes.

5.2.6.13Negative control should not show growth up to 7 days.

5.2.6.14If any of the inoculated sterile strips of empty chamber, minimum load and maximum load show growth within 7 days of incubation then lab oven performance is unsatisfactory. Call Service Engineer for maintenance and put label “UNDER MAINTANANCE “. After maintenance perform the whole procedure as mentioned above until satisfactory.

5.3       Frequency: Calibration of lab oven shall be carried out once in six months ± 7 days or any major accessories are change.

5.4       Temperature Mapping of Lab Oven:

5.4.1    Lab oven shall be mapped with temperature scanner probes.

5.4.2Arrange 8 temperature probes in the lab oven as shown in diagram annexure-1.

5.4.3Close the door tightly and set the temperature to 181º C on the control panel of the lab oven.  Cycle shall be run at 181º ± 2º C for 2 hours and set the safety knob temperature to 5º C   above the set temperature.

5.4.4Check the ventilator at the right hand side of the chamber is closed.

5.4.5Note the starting time of the lab oven in observation report.

5.4.6Record the digital display temperature of the lab oven and all probes of the scanner reached 181º C. Run the cycle up to 2 hours.

5.4.7Record the readings of digital display temperature of lab oven during hold time at 30 min’s interval in formatxxxxx.

5.4.8In data logger record the temperature of all the eight probes at 1 min interval.

5.4.9If the temperature readings of the scanner found satisfactory within the 181º ± 2 º C then lab oven is complies. If not complies with the above specifications then label it ‘UNDER MAINTANANCE’ and call service Engineer/ Manufacturer. After the rectification of lab oven temperature mapping shall be repeated.

5.4.10Frequency: Temperature mapping of the lab oven shall be done once in a year with ± 15 days by external agency / with internal data logger.

6.0       Related Documents: Nil.

Microbiology, calibration of lab oven, sterilization