Introduction
17.1 This chapter contains detailed procedures for tests specific to machines designed to process loads by exposure to low-temperature steam (LTS disinfectors) or low-temperature steam and formaldehyde (LTSF sterilizers). Schedules, prescribing which tests are to be carried out and when, are set out in Chapter 4 (for validation tests) and Chapter 5 (for periodic tests).
17.2 Machines are usually designed for both LTS and LTSF. These processes have similar characteristics and a machine incapable of meeting the LTS
requirements will not normally meet the LTSF requirements. Note that some LTSF machines expose the load to a series of pulses of sterilant rather than a continuous holding time.
17.3 Attention is drawn to the safety Information presented in Chapter 1 and the detailed safety precautions discussed in Part 4.
Chamber overheat cut-out test
17.4 This test is designed to show that the overheat cut-out mechanisms for the chamber and jacket will prevent the temperature of the chamber walls and free space from exceeding 80°C. Where two temperature control mechanisms are fitted (for the jacket and the chamber) the test should be done twice, with each mechanism inactivated alternately.
17.5 Temperatures should be recorded by independent measuring equipment as described in Chapter 6. If an LTSF sterilizer is being tested, the LTS cycle should be selected. If an LTS cycle is not available, the primary material for generating formaldehyde should be replaced with an inert substitute (see paragraph 1.29). The chamber should be empty except for the usual chamber furniture.
17.6 Place 12 temperature sensors in the following positions: a. one in an active chamber discharge (see paragraph 6.26);
b. five on each of the two chamber side walls (one at the approximate centre and four adjacent to the corner positions of the usable chamber space); c. one on the plane of the usable chamber space (not on the wall) at a point
17.9 The test should be considered satisfactory if the following requirements are met:
a. the cut-out device operates and causes the heat source to be isolated from the machine and the operating cycle to advance to the drying stage;
b. none of the measured temperatures exceeds 80°C;
c. at the end of the cycle the door remains locked and a fault is indicated.
Chamber wall temperature test
17.10 This test is designed to show that the air removal stage will not start until the chamber walls are heated to within 2°C of the selected operating temperature. If an LTSF sterilizer is being tested, the LTS cycle should be selected. If an LTS cycle is not available, the primary material for generating formaldehyde should be replaced with an inert substitute (see paragraph 1.29).
17.11 Temperatures should be recorded by independent measuring equipment as described in Chapter 6. The chamber should be empty except for the usual chamber furniture.
17.12 Place 12 temperature sensors in the positions described for the chamber overheat cut-out test (see paragraph 17.6).
17.13 Select and start the LTS operating cycle.
17.14 The test should be considered satisfactory if the following requirements are met:
a. the air removal stage of the operating cycle does not start until the temperatures measured by the 10 sensors attached to the chamber side walls are within 2°C of the selected operating temperature;
b. after the first 5 min of the holding time all the temperatures measured in the chamber are within –0°C + 5°C of the temperature measured in the active chamber discharge.
Thermometric test for a small load
17.15 If an LTV sterilizer is being tested, the LTS cycle should be selected. If an LTS cycle is not available, the primary material for generating formaldehyde should be replaced with an inert substitute (see paragraph 1.29).
17.16 Temperatures and pressures should be recorded by independent measuring equipment as described in Chapter 6.
17.17 Place a standard test pack (see paragraph 7.27) in the chamber with the bottom of the pack supported 100-200 mm above the centre of the chamber base.
a. one in an active chamber discharge (see paragraph 6.26);
b. one at the approximate centre of the test pack (the wire from the sensor should be carefully arranged to prevent steam tracking along it);
c. one placed 50 ± 5 mm above the approximate centre of the upper surface of the test pack.
17.19 Connect a pressure recorder (or test gauge) to the chamber.
17.20 Select the LTS cycle. Ensure that the process temperature is set to 73°C (corresponding to a sterilization temperature of 71°C). Start the cycle.
17.21 If a test gauge is being used, measure and note the chamber pressure at the approximate mid-point of the holding time.
17.22 The test should be considered satisfactory if the following requirements are met:
a. the requirements of the automatic control test (see paragraph 12.13) are met;
b. the holding time, determined from the measured temperatures, is not less than that specified in Table 8;
c. during the holding time:
(i) the measured temperatures are within the temperature band specified in Table 8;
(ii) the temperature measured above the test pack is within 4°C of the temperature measured in the active chamber discharge;
(iii) the temperature measured in the centre of the test pack is within 2°C of the temperature measured in the active chamber discharge;
(iv) the indicated and recorded chamber temperatures are within 1°C of the temperature measured in the active chamber discharge;
(v) the indicated and recorded chamber pressures are within 0.05 bar of the measured pressure;
d. for sterilizers using vacuum as the sole method of drying: (i) the duration of the drying stage is not less than 3 min;
(ii) the chamber pressure at the end of the stage does not exceed 50 mbar absolute;
e. at the end of the cycle the sheets are sensibly dry.
which may be processed in the machine, and is used to demonstrate that, at the levels at which cycle variables are set, rapid and even penetration of steam into the centre of a load occurs and disinfecting conditions are achieved.
17.25 Temperatures and pressures should be recorded by independent measuring equipment as described in Chapter 6.
17.26 Place a standard test pack within the chamber in a position identified by the manufacturer as the most difficult to disinfect. This will normally be in the
approximate centre of the chamber. Load the rest of the usable chamber space with stacks of sheets as described for porous load sterilizers (see paragraphs 13.17, 13.20).
17.27 Place three temperature sensors in the following positions: a. one in an active chamber discharge (see paragraph 6.26);
b. one at the approximate centre of the test pack (the wire from the sensor should be carefully arranged to prevent steam tracking along it);
c. one below the approximate centre of the top sheet of the test pack. 17.28 Connect a pressure recorder (or test gauge) to the chamber.
17.29 Ensure that the LTS operating cycle is set to an operating temperature of 73°C. Start the cycle.
17.30 If a test gauge is being used, measure and note the chamber pressure at the approximate mid-point of the holding time.
17.31 The test should be considered satisfactory if the following requirements are met:
a. the requirements of the automatic control test (see paragraph 12.13) are met;
b. during the holding time:
(i) the measured temperatures are within the temperature band specified in Table 8;
(ii) the temperature measured in the centre of the test pack is within 2°C of the temperature measured in the active chamber discharge;
c. at the end of the test the sheets are sensibly dry;
d. the total cycle time is within the performance class stated by the manufacturer.