Edition #5 - Reducing Injury Risk Through Thoughtful Safety Mechanism Design

In the last newsletter we looked at how fail-safe design is the ideal. However, it is not always possible to achieve in all situations. In many cases, additional safety mechanisms are required to reduce risk when the primary design can't fully eliminate it.

A safety mechanism is any added feature, mechanical, electrical, or visual, that reduces the likelihood of harm. It acts as a backup to core design functions and is especially important where the consequences of failure are severe.

Examples include:

• Physical guards over moving parts
• Interlock switches
• Automatic shutdown systems
• Pressure relief valves
• Latches or catches
• Visual indicators (e.g., colour tabs or flags)
• Alarms or buzzers

These should not be relied on as the only protection, they are most effective when paired with inherently safe design.

Key Considerations for Good Safety Mechanisms:

• Visibility and Feedback

For mechanical safety devices, such as latches, catches, or locks, it is essential that their status is immediately clear to the user. Users should be able to determine at a glance whether the mechanism is properly engaged or deployed.

• Self-indicating Mechanisms

Favour self-indicating designs wherever possible. For example, a latch that produces a clear audible click and visibly locks into place, similar to a seatbelt, provides intuitive feedback to the user.

• Visual Indicators

If the mechanism’s state isn’t inherently obvious, incorporate a built-in visual indicator. This indicator should be integrated directly into the mechanism, if at all possible, not added separately. Independent indicators that can fail, misalign, or disconnect from the mechanism pose a risk by giving users a false sense of security. Visual cues might include colour changes (e.g., red/green), moving tabs that shift position when engaged, or other unmistakable signals. The critical point is this: the user should never be left guessing whether the product is safe to use.

• Performance Across Configurations

Safety mechanisms must be effective across all intended (and reasonably foreseeable) use conditions of the product. For example:

• A guard must stay in place regardless of whether the product is upright, on its side, or mounted in an unusual orientation.

• A childproof lock should work whether a cabinet is full or empty, upright or tipped.

• A shutdown mechanism should still engage in edge-case scenarios like overheating, power surges, or unusual user actions.

It’s not enough to test a mechanism in one configuration. Robust safety design involves anticipating variability in how, where, and by whom a product will be used.

• Built-in Redundancy

In critical applications, it may also be necessary to build in redundancy—that is, using more than one mechanism or layer of safety. For example, a machine might have a guard and an interlock switch that disables movement when the guard is removed. If one fails, the other still offers protection.
Robust safety mechanism design is about more than just ticking compliance boxes, it’s about actively protecting users in real-world conditions. A good safety mechanism should be:

• Intuitive – Users shouldn’t need a manual to understand it.

• Reliable – It works in all expected conditions.
• Integrated – Part of the product, not an afterthought.
• Communicative – Clearly signals its status to the user.

When well-executed, safety mechanisms can significantly reduce the risk of injury and enhance user confidence in the product.
In the next newsletter we will look at how to design out some of the most common product failures that lead to injury.