5.18.1 Monitoring Test Chamber Parameters
It is good scientific and engineering practice to monitor chamber conditions to ensure the chamber settings are correct, and the desired environmental conditions within the chamber are being maintained within specified tolerances throughout the duration of the test. An environmental engineering specialist should work with the customer to tailor monitoring requirements to the customer's needs. Considerations include:
- a. The frequency of monitoring may vary depending on the data requirements and how the data are to be used. Monitor test parameter levels throughout the test at intervals that are meaningful for the item under test such that a failure to maintain prescribed parameter levels may be corrected without jeopardizing the validity of the test.
- b. Establish an alarm system to be triggered by parameter levels that stray out of tolerance beyond acceptable limits.
- c. To provide proof of parameter level maintenance, keep a manually- or electronically-produced log of parameter levels. Exact parameter monitoring intervals and exact methods of recording parameter levels may vary for different methods and for different items being tested using a specific method. In some instances, monitoring chamber parameters may be required only at long intervals (15-minutes or even several hours). In others, continual, non-stop recording may be necessary.
- d. The technology involved in recording parameter levels may involve visual checks at prescribed intervals, real time continuous recording such as a circular chart, periodic recording on a device such as a data logger, or other techniques established in a contract or agreed upon by the tester and the customer.
- e. From a quality assurance standpoint, the intervals at which monitoring should occur depend on how meaningful the interval length is to the customer, who should be provided with monitoring records that are no longer, or shorter in interval than the customer’s needs.
5.18.2 Monitoring the Item Under Test
It is equally important to monitor the test item itself to record the effects of the chamber environment on the physical condition or performance of the item under test. The reason for such monitoring is to ensure that pertinent changes in the condition of the item under test are captured at relevant intervals throughout the duration of the test so that meaningful test item failure analyses may be performed. Consider the following:
- a. The tester must meet contractual or other monitoring requirements established by the customer to fulfill test data needs.
- b. The frequency of monitoring will vary depending on the data requirements and how the data are to be used. For example, during conditioning, it may be desirable to monitor the condition of the test item infrequently because the information gathered during this period of testing, though important, may not be highly critical. However, during cycled static testing or system performance testing, the frequency of monitoring the test item may be higher at the beginning of a test to capture initial, fast-occurring degradation. Other minimum intervals may be set to capture transient events that may occur at any time during the test.
NOTE: If the test item is intended to be occupied during test events, consideration should be given to installation of sensors to monitor health hazards such as VOCs, CO, and Phthalates due to potential off-gassing/out-gassing.