FAQs

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What is the reason for a different color on labels/ class 6 indicators near the chamber walls of a sterilizer and a different color on the inside of the packs? The BMS strip shows a proper color change when placed in the same load in the worst load case. What is the solution to solve this problem?

Close to the walls you get superheation, which is detected by Gke labels and Gke class 6 indicator. Inside the packs and in the PCD you compensate overheation with created condensate.
First of all you have to test, if our proposal of superheation close to the walls was correct. Please measure with thermo-sensors at the wall. The reason could be superheated steam being introduced or the pressure in the jacket is higher than the pressure in the chamber. The jacket pressure should be almost identical to the chamber pressure, otherwise the walls are warmer than the steam inside the sterilizer chamber creating superheation close to the walls.

The second reason could be centralized steam supply with reduction valves without cooling possibilities between reduction valve sterilizer inlet..

What is the reason for a different colour on labels/ class 6 indicators near the chamber walls of a sterilizer and a different color on the inside of the packs?

The BMS strip shows a proper colour change when placed in the same load in the worst load case.

Can one use an unwrapped cycle in the Operating Room for an implant?

We would not recommend to use flash sterilizers for implants. The risk of recontamination is too high. Normal sterilization with double packing is recommended.

How do you test the quality of the Indicators being supplied ?

As per EN ISO 111450 part 1, an indicator should not change color to the end color in the absence of steam. The recommended practice is to put the said indicator in a bakery oven or a dry heat sterilizer at 140 C and keep a holding time of 30 mts. At the end of the process the indicator strip is allowed to change color. However the color change of the indicator should not be to the end color.

How long can a product remain sterile once sterilized unwrapped or in a flash cycle?

The goods remain sterile until they are contaminated from outside. This depends on the handling of non-wrapped goods. 1 – 2 hours being wet is no problem.

For general cleaning one only requires cleaning., Why?

In Europe in washer disinfectors cleaning is done with cleaning solutions, the disinfection is carried out by thermal disinfection (water 90 – 95°C, 5 – 10 min).
What are the requirements for biological monitoring and what guidelines should I consider.
You have to differentiate between solid instruments and porous loads and basic validation of your processes and routine monitoring:

1. For basic validation of solid instruments and porous loads biological indicators on top of the instruments or inside of the porous loads are suitable.
2. For the validation of hollow loads direct inoculation inside of the loads and after sterilization incubation in a microbiological lab is necessary
3. For routing monitoring of solid instruments and porous loads chemical indicators class 5 or 6 in the packs are suitable or a Batch Monitoring System can be used.
4. For routine monitoring of hollow devices you must use a batch monitoring system calibrated against the most difficult hollow device.

What is difference between cleaning solution & disinfection solution?

Cleaning solution has the job to dissolve non water soluble proteins to clean the surfaces, the disinfection solution has the job to kill the germs. However most of the cleaning/disinfection solutions do both.

What is the difference between type A and type B hollow loads?

According to the definition type A hollow objects are instruments with an open cavity on only one side where the ratio of length to diameter of the cavity is greater than or equal to 1 and less than or equal to 750 (1 = L/D = 750) and where the length of the cavity is not greater than 1500 mm (L = 1500 mm); or, alternatively, instruments with an open cavity on both sides where the ratio of length to diameter of the cavity is greater than or equal to 2 and less than or equal to 1500 (2 = L/D = 1500) and where the length of the cavity is not greater than 3000 mm (L = 3000 mm). Type B hollow objects, on the other hand, are instruments with an open cavity on only one side where the ratio of length to diameter of the cavity is greater than or equal to 1 and less than or equal to 5 (1 = L/D = 5) and where the diameter of the cavity is greater or equal to 5 mm (D = 5 mm); or, alternatively, instruments with an open cavity on both sides where the ratio of length to diameter of the cavity is greater than or equal to 2 and less than or equal to 10 (2 = L/D = 10) and where the diameter of the cavity is greater or equal to 5 mm (D = 5 mm).

The Cavity diameter (D) / Length (L) chart below shows the areas relating to type A (in blue) and type B (in orange) hollow bodies with an open cavity on only one side (for those with an open cavity on both sides, for any given cavity diameter, double the length to obtain the equivalent diagram). The space above these areas relates to those bodies where the ratio of length to diameter of the cavity is too big for them to be sterilized even with B cycles; the space below relates to bodies that are not hollow but solid.

What is the Helix Test for?

Its purpose is to check the degree of steam penetration in the case of hollow objects and the efficacy of the air removal system. The test uses a Teflon tube open at one end only (length 1.5 m, internal diameter 2 mm), ending with a Teflon capsule, containing a chemical process indicator. EN 13060 requires for purposes of approval the employment of this apparatus to test cycles for sterilizing hollow load A (for example B cycles). The test is positive if the chemical indicator changes colour in line with the information given by the producer.
The thermometer test described in the answer to F.A.Q. What is the sterilization temperature band? is not required for hollow load A, in that it is not possible to make a precise measurement of the temperature reached at the back of the cavity of the apparatus described above.

What is a process evaluation system for?

EN norms require the presence of a process evaluation system and/or recorder. The former must automatically monitor the factors essential to ensuring sterilization and must indicate to the operator if the cycle is acceptable or not. In particular, a process evaluation system should answer the same questions as those a well-trained operator would pose when examining the record of the cycle to say whether it has been completed correctly or not:
· Was the pressure in the pre-vacuum phase and the succeeding vacuum pulses low enough?
· Was the time taken to reach it within the allowed limits?
· Was the pressure at the steam peaks high enough?
· Was the time taken to reach it within the allowed limits?
· Was the pressure during sterilization within the allowed limits?
· Was the time taken to reach it within the allowed limits?
· Was the temperature during sterilization within the allowed limits?
· Did the sterilization last long enough?
· Was the pressure in the drying phase low enough?
· Did the drying last long enough?
In a word, he has to be able to identify specific anomalies relating to the process or the autoclave.

What are the pre-vacuum phase and any vacuum pulse phase for?

These are necessary for the removal of air from the autoclave chamber, given that at any given pressure and temperature the density of air is around 1.5 times that of steam, such that any air present during sterilization settles in the lower part of the chamber and creates so-called “air pockets”, where the temperature is not controlled and this is potentially deleterious as far as sterilization quality is concerned.

What is the sterilization temperature band?

EN norms lays down that during sterilization the following nine temperatures – eight measured at different points within the load and the unoccupied space remaining in the chamber and the last a reading taken on the saturation vapor curve according to the pressure measured in the chamber – must be above the sterilization temperature, but not by more than 4 °C (e.g. for a cycle at 134 °C the readings must be between 134 and 138 °C, the sterilization range). In addition, there must not be more than a 2°C difference between any one reading and another at any given time. This guarantees that the conditions necessary for sterilization are kept constant and uniform throughout the period of exposure and, by means of a comparison of temperature to pressure on the saturation vapor curve, that the air has been properly removed prior to sterilization.

What are the main features of steam sterilization?

Heat is the best and most used sterilization method and pressurized, saturated water vapor is the most efficient method of heat transmission. That is why steam sterilization reduces the time and the temperature needed for the treatment: at 134 °C an exposure of only 4 minutes is sufficient, at 121 °C a time of 15 minutes is enough. In addition, steam sterilization creates no toxic or dangerous residues on objects and does not damage instruments (provided that they can withstand the temperatures reached).

What is the difference between disinfection and sterilization?

Disinfection destroys all the micro-organisms present in a given environment apart from spores: an object that has been disinfected properly may still transmit a pathogenic micro-organism. Sterilization, on the other hand, is the complete elimination of all micro-organisms including spores.

Why do chemical indicators and biological indicators pass when the cycle print out shows an aborted cycle?

One has to remember the data recorder that actually creates the print out does NOT control the cycle, but just records the data generated by sensors and air detectors located throughout and around the chamber.

The cycle is controlled by the solenoid valve which controls the steam charges and vacuum pulses and the entire cycle including time temperature / pressure. In a sterilizer if an abort occurs, a micro chip over rides everything and takes the cycle immediately into the exhaust phase and then into the drying phase to finish the process, however, if the abort takes place during the holding time, the micro chip will stop the cycle and go to exhaust and drying, but BI’s, CI’s, and PCD’s may well have been exposed long enough to have completed the necessary color changes or kill, to show a pass condition as explained further in this paper.

A cycle can abort in the conditioning phase, the pre-heat or come up phase, the holding time, the exhaust phase or the drying phase, because the defined or set parameters have not been met.

The most common aborted cycle takes place during the pre-heat or come up phase of the cycle.

Users must realize that once the temperature has reached or passed 100/1100C that integration of BI’s, CI’s, inside and outside of packs and PCD’s (including Bowie Dick Tests) begins to take place and, irrespective of when the cycle data logger indicates an aborted cycle, the process will continue (unless there, is a microchip installed as referred to above) until the chamber pressure is reduced back to atmospheric pressure. This means that the print out data stops, but the cycle will go through its holding time at temperature (which may be reduced to 2.5 minute) and the proceed into the exhaust phase when the chamber pressure is reduced back to atmospheric pressure and the door can be safely opened. If the cycle aborts during the heat up phase, the chamber is under pressure and the door cannot under any circumstances, be safely opened. In any event, the internal pressure, of the chamber will not allow this to happen anyway, and it will not let this take place until atmospheric pressure in the chamber had been achieved.

To give a better understanding of the concept and the principle involved, consider the following analogy.

A locomotive train is traveling at 100kph and the emergency brakes ate applied. The train cannot possibly stop at the point where the brakes are applied and the train continues its forward momentum until the full effects of the braking motion bring the train to a stop which could be anything upto a kilometer from the point of application of the brakes.

A sterilization cycle is no different, because the data logger prints, “cycle aborted” in the pre-heat phase, and because the cycle has progressed through 100/1100C, it will continue its programmed path (unless there is a micro chip installed when the cycle will go to exhaust immediately) until atmospheric pressure has been achieved within the chamber

This means that the cycle has to go through a holding time and into the exhaust phase to bring the chamber back to atmospheric conditions. This in turn means that all BI’s, CI’s, inside and outside plus PCD’s (including Bowie Dick Tests) will show that the cycle did in fact go through the sterilization or holding time because they will show a pass by changing to the colour change indicated on them, or by their destruction. Remember, the date logger does NOT control the cycle and, like the train trying to stop its forward momentum once the brakes have been applied, the sterilization cycle cannot stop in the pre-heat phase above 1100C and must continue until the chamber is back to atmospheric pressure. The cycle cannot “leapfrog” the holding time into the exhaust phase to achieve atmospheric pressure, as it is programmed to follow a pre-determined path, which cannot be changed by the data logger aborting. If the sterilizer has a microchip installed then it will go to exhaust irrespective of where the cycle process is at when the abort takes place.

Because there is an element of doubt regarding the efficacy of the cycle due to the lack of information on the print out, the load should be rejected and re-processed if there is a “Cycle Abort” printed, though the CI’s and BI’s and PCD shows a PASS.

Can chemical Indicators class 4, 5 & 6 recognize entrapped air inside complex Instruments?

Chemical Indicators with the correct stated value (temperature) and end point (time) can only recognize entrapped air if they can simulate the inside of the instrument therefore, in their current format, Chemical Indicators can only give information at the point at which they are placed within the pack. Class 4-5-6 chemical indicators are NOT Process Challenge Devices, as they cannot simulate worst case situations in validation load, nor do they have x-ray vision, so they cannot replicate a Process Challenge Device.

Can an air detector replace the Bowie and Dick Test?

No, the air detector cannot recognize entrapped air inside a pack but only monitors condition in the free space of the chamber. The quantity levels at which non condensable (air) gases become critical depend on the goods to be sterilized. For example, a Bowie Dick 7kg linen pack signals an error by means of an inserted indicator sheet or by growth of inserted biological Indicators, if 150-200ml of air has a total inner volume of only 3.14ml. Therefore 0.314ml of non-condensable gases will block 10cm of the tube length to steam penetration, thus preventing effective sterilization of this instrument or tubing at this location.

Why is the Quality of Steam so important?

Poor quality of contaminated steam can generate wet steam, and more importantly, non-condensable gases like air. Non-condensable gases will impede the sterilization process and prevent sterilization from taking place.

Why is Air Removal so Important?

If air is not removed from inside “hollow instruments”, steam cannot penetrate and reach the inner surfaces of any “hollow complex Instruments” therefore the Instrument would remain un-sterile as the required parameters for moist heat sterilization have not been achieved and the encapsulated air changes the process from moist heat to dry heat with totally different parameters i.e. 1600C for 2hrs.

This section is dedicated to providing authentic information on instrument reprocessing. You can ask us questions, answers for which you need and are not found in this section. It will be our endeavour to provide you with the correct answer in the quickest possible time. We willalso be publishing all the fresh questions that you may ask in this section.