2. When placing articles to be sterilized in the chamber, leave room so that the steam can pass around and about each object. Do not pack articles too close together and do not jam the autoclave full.
This is probably the commonest mistake made in operating hospital sterilizers. It amounts to taking a serious and unnecessary risk, for when an autoclave is packed too closely and too full, there is no certainty that all articles will be heated enough to be sterilized.
It is better to place articles to be sterilized in many small containers than in a few large ones. Close and seal the door as tightly as possibly.
3. Allow the steam to enter the jacket until the gauge shows a pressure of about 15 pounds, Keep the valve controlling the exhaust from the inner chamber open, so that the air in the chamber may escape Now allow the steam to enter the inner chamber by manipulating the proper valve, meanwhile leave the exhaust valve open.
Allow the steam to run in for several minutes with the exhaust open, until nothing but dry steam comes out of the exhaust. This is necessary because all the air in the chamber must be driven out and entirely replaced by steam.
Otherwise, although the gauge might show a pressure of 15 pounds, it would not be 15 pounds of steam, but a mixture of steam and air and this mixture could not be hot enough to sterilize.
When all the air has thus been driven out and only steam comes through the exchaust, close the exhaust valve almost but not quite completely, so that a small amount of steam may escape from it throughout the sterilization process.
When the valve is nearly closed, the pressure of steam in the chamber will quickly reach the required 15 pounds. The gas under the boiler may be lowered or the steam supply shut off enough so that the pounds pressure is constantly maintained.
4. Note the time when the steam in the chamber reaches the pressure of 15 pounds and maintain this pressure continuously for the next 20 to 30 minutes.
5. At the end of this period turn off the gas under the boiler, or shut off the steam supply and allow the autoclave to cool down. When only linens, dressing or similar materials are being sterilized, the exhaust valve may be opened to allow the steam to escape quickly; but if any liquids are present in tubes or flasks, the exhaust valve must not be opened at all until the pressure has returned to 0, for otherwise the liquids will boil violently and cotton plugs will be blown out.
Some autoclaves are made so that a slight vacuum (4 or 5 pounds) may be produced in the chamber before the exhaust valve and door is opened and the articles removed.
This helps to make the articles dry, but it is not necessary for if the autoclave is running properly, cotton plugs, dressing, and other objects will come out of the autoclave hot and quite dry.
It is a practice in many hospitals to place in each load of material to be sterilized a “sterilizer control” or indicator. This is a small glass tube, with a string attached, containing a chemical which changes colour at the sterilizing temperature.
It should be placed in the center of a large package in the midst of other articles. After sterilization, the tube may be pulled out by its attached string and examined.
If the expected colour change has occurred, this indicates that the sterilized temperature was attained at least for a short time, and it is certain proof that the particular package from which the tube was drawn has been through the sterilizer.
Another method often employed is to place in the autoclave a thermometer which will show the highest temperature reached. Too much dependence should not be placed upon these controls, however.
They do not show whether the necessary temperature was constantly maintained for a sufficient length of time. The only safe and proper way is to operate the autoclave most carefully at all times, observing all the precautions outlined above.