When is cooling gear not required according to work length and dry bulb temperatures?

The correct choice indicates that cooling gear is not required for work lengths greater than 4 hours at dry bulb temperatures above 90 degrees Fahrenheit. This reflects the established safety and health standards that account for prolonged exposure to high temperatures. Typically, the risk of heat-related illnesses increases significantly with longer durations of work in elevated temperatures. Therefore, specific thresholds for duration and temperature have been set to ensure safety.

In this case, as the work length exceeds 4 hours and the temperature is above 90 degrees Fahrenheit, the body's ability to regulate temperature becomes compromised, necessitating the use of cooling gear to prevent heat stress.

The context of the other scenarios highlights less critical conditions. For instance, shorter work durations or cooler dry bulb temperatures may not require cooling gear, as workers are likely able to manage their body heat within safe limits. These safety measures are designed to protect against heat exhaustion and other thermal stress-related conditions.