What are the potential effects of oxygen-deficient atmospheres at 15-19% by volume?

At oxygen levels ranging from 15-19% by volume, the body begins to experience a range of physiological effects due to reduced oxygen availability. The correct answer highlights that individuals may encounter decreased ability to work strenuously and impaired coordination. This occurs because the body relies on adequate oxygen levels for effective muscle function and cognitive processes. When oxygen levels drop below the normal range (which is around 20.9% in the atmosphere), symptoms of impairment can manifest.

In this range of oxygen deficiency, individuals may feel more fatigued with physical strain, as the respiratory and cardiovascular systems struggle to meet the oxygen demands of the body. Coordination may also suffer because the central nervous system requires oxygen to function optimally, affecting motor skills and reflexes. Hence, the correct choice reflects how even mild reductions in oxygen can impact physical performance and coordination.

The other options focus on more severe or different types of effects than those typically associated with mild oxygen deficiency. Loss of consciousness can occur at much lower oxygen levels, while frostbite and increased heart rate are related to different physiological responses. Frostbite, for example, is associated with extreme cold rather than oxygen deficiency, and while an increased heart rate may occur in response to some stressors, it is not a