What must be done before adding any attachments to a direct reading instrument?

Adding attachments to a direct reading instrument should always be preceded by calibration of the instrument. Calibration ensures that the instrument is providing accurate readings in accordance with the manufacturer's specifications. If the instrument has not been calibrated properly, any data obtained after attaching different components may be flawed, leading to inaccurate measurements. Therefore, it is critical to ensure that the baseline accuracy of the instrument is established first.

This practice is essential for ensuring safety and reliability when monitoring for hazardous materials, as it directly affects the response actions taken in hazardous environments. Proper calibration also accounts for changes in the environment and variations in the instrument's performance over time.

In addition, the other considerations such as inspecting attachments for damage, checking the alarm, or allowing the meter to return to background readings are indeed important steps in preparing and operating a direct reading instrument, but they should follow the crucial step of calibration to guarantee the instrument’s effectiveness and reliability.