What is a critical safety precaution when working with hydraulic systems?

When servicing hydraulic systems, releasing pressure before beginning any work is a critical safety precaution because hydraulic systems operate under high pressure, which can pose significant safety risks. If pressure is not relieved, there is a danger of unexpected fluid ejection, which can lead to personal injury or accidents due to the sudden release of stored energy in the system.

Relieving pressure ensures that components can be safely accessed and serviced without the risk of hydraulic fluid spraying uncontrollably, which can cause burns or injuries. It's essential to follow proper lockout and tagout procedures to ensure that all hazards are addressed before maintenance begins.

This precaution contrasts sharply with the other options, which do not contribute to safe practice in the same manner. Increasing fluid viscosity or using thinner fluids can affect the system's performance but does not directly address safety. Overfilling the hydraulic reservoir can lead to fluid spillage and increased pressure, which is also unsafe. Therefore, releasing pressure is the most critical step to ensure safety when working with these powerful systems.