Exam Study Guide: Oxygen Levels

Exam Study Guide: Oxygen Levels

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When faced with a licensing exam, don't struggle with test anxiety! Use the question below and others from our Exam Study Guide series to study and prepare for exam questions. Take a look at this sample water treatment licensing question along with an explanation of the correct answer.

Sample question:

What is the percent oxygen of normal air at sea level?

A) 20.9 percent
B) 19.5 percent
C) 15 percent
D) 18.5 percent

Answer: Normal air is mostly nitrogen and oxygen with a few traces of other inert gases. At sea level, normal air is about 78.1 percent nitrogen and 20.9 percent oxygen. When working in a confined space, it is important to continually monitor the atmosphere to confirm the oxygen level has not decreased below 19.5 percent. Oxygen levels that are below 19.5 percent can cause shortness of breath or even death depending on how low the oxygen level is.

So, the correct answer is A.

Reference: Water Treatment Plant Operation. 5th Edition, Volume ll, California State University, Sacramento. Page 480

About the author
Drew Hoelscher is the program director of drinking water operations at the Environmental Resources Training Center (ERTC) in Edwardsville, Illinois.


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