Backflow Prevention Practice Exam

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Confined space air monitors will sound if the oxygen percentage is less than _____%?

18.0
18.5
19.0
19.5

The correct answer is: 19.5

The correct choice is based on safety standards for confined spaces, which typically consider an oxygen level of 19.5% as the lower limit for safe working conditions. Below this threshold, the atmosphere is deemed unsafe for personnel without proper respiratory protection or ventilation due to the risk of hypoxia, which can impair cognitive functions and physical abilities. Monitoring devices are calibrated to trigger alarms when oxygen levels drop to the 19.5% mark, alerting personnel to the potential danger. This standard is widely adhered to in industrial safety regulations to maintain a safe working environment. While other values might be used in certain contexts, the 19.5% figure reflects the accepted safety minimum from which to gauge air quality in confined spaces. Thus, a reading below this percentage indicates the environment is hazardous, prompting immediate safety measures to be implemented.