Few qualification facts of Sterilization and Depyrogenation tunnel

Dry heat is used for sterilization instead of the much more efficient moist heat because some materials are sensitive to moisture. Dry heat is often used to ensure that glass and other laboratory equipment is free of pyrogenic material. The process of sterilization within a chamber or hot air tunnel is a critical process and there is a regulatory requirement for validation of the process in most countries. Validation is defined as the documented procedure of obtaining, recording and interpreting results to ensure that the dry heat sterilization process has been and will be consistently effective. Dry heat sterilizer validation consists of accurately measuring the temperature at critical points within the sterilization chamber throughout the process. Dry heat process generally employs a temperature between 250°C and 400°C for varying time. The sterilizer is required to heat all parts of its load up to the specified temperature for a specified period long enough to achieve the desired sterility.

Snap Shots of Qualification:

Set points: Record the ammeter values and differential pressures.

Differential Pressure:The Tunnel zones are balanced per the manufacturer specifications. Air does not move from dirty to clean.

Air Velocity:Critical Areas should have laminar airflow of 90 fpm ± 20%, or 28 m/min ± 20%

Laminarity Smoke Testing:The entry hot and cooling zones demonstrate laminar air flow.

Smoke flow direction with the Tunnel Sterilizer 

Total Particulate Counts:The oven must meet specifications for total particulates, . less than or equal to 100 for less than 0.5 micron per ft3 or less than or equal to 3,500 for less than 0.5 micron per m3 and 0 for 5 micron per m3

Thermocouple Calibration: All thermocouples will calibrate within ± 0.5*C of the reference temperatures before protocol execution and verify within ± 0.5*C of the high reference temperature after protocol execution.Eighty-five percent of thermocouples used must be operational upon completion of the study.All critical thermocouples (i.e. thermocouples with specific acceptance criteria, such as cold spots or adjacent to a controller)must be operational upon completion of the study.

Temperature Mapping: During the mapping period, the temperature readings for the temperature recording chart and the average chamber temperature for Tunnels at 250*C and greater are consistently ± 15.0*C of each other throughout the study:Temperature range among thermocouples for Tunnels at 250*C and greater, for each five minute interval, is ± 15.0*C of the average temperature throughout the study. The average temperature for Tunnels at 250*C and greater at each interval is ± 15.0*C of setpoint temperatureCalculation of tunnel speed and cycle timing is a important issue during validation of Sterilization and Depyrogenation  tunnel. We can solve with a easy two steps mention below.

Temperature Mapping, Specific Loads:To determine cold spots.Monitor Tunnel differential pressure during the depyrogenation period.

Endotoxin Studies, done in triplicate: Inoculate glassware or vials with a minimum of 5,000 EU of E. coli lipopolysaccharide. All inoculated glassware placed must demonstrate, at minimum, a three-log reduction in endotoxin.

Positive controls must demonstrate a minimum recoverable 1,000 EU, per Validation of Dry Heat Processes Used for Sterilization and Depyrogenation, PDA Technical Report Number 3.Negative controls (pyrogen free water) must not exhibit a level of endotoxin above the minimum sensitivity of the reagent used.Minimum cumulative FH location will be determined for informational purposes only.Distribution thermocouples are within a range of ± 15.0* C from the mean of the distribution thermocouples.

Example for Conveyor speed calculations,
# Vial Dimension 50 mm
# Speed of conveyor 135 mm/min
# Length of the tunnel 457 mm
# Width of the tunnel 1200mm
No’s of vial lying vertically = 1200 mm/ 50 mm = 24 vials
No of vial lying horizontally = 457 mm / 50 mm = 09 vials
Total vial capacity in the tunnel sterilization zone = 24x09 = 216 vial 
If 50 mm moved 09 vial will released from hot zone. In case of machine speed 135mm/min means
(9x135)/50 = 24 vials will come from hot zone/per min
Time spend by the each vials id 135 mm/50 mm = 2.7 min