Lesson 5 - Health and Safety SAQ
This lesson allows you to test yourself on the material covered in the lesson on Health and Safety and determine the level to which you have met the learning outcomes.
Suggested Response - Q3
* If an employee, who tips malt from sacks into an industrial sieve, is exposed to a maximum of 12 mg/m3 of respirable dust for a period of up to two hours a day or over, are they exceeding the typical WEL (workplace exposure limit)? Show your workings.
Response:
No. Grain dust is typically assigned a WEL of 10 mg/m3, 8-hour time-weighted-average (TWA). Over any 15-minute period the exposure should not normally exceed 30 mg/m3. The exposure in the question (12 mg/m3) is below the short-term exposure limit of 30 mg/m3.
Next you need to work out the TWA, by converting the two-hour exposure to the equivalent average over eight hours. The example above is 12 mg/m3 over two hours, which would equate to 3 mg/m3 over eight hours (12*2/8=3). This is well below the eight-hour WEL of 10 mg/m3.