3.2 How to Choose a Control

There is an order of preference, the hierarchy of risk control. Controls near the top rely much less on people doing something and can protect larger numbers of people. Controls near the bottom depend on behaviour and are more likely to fail.

1. Eliminate the hazard

This is the most effective control. Remove the hazard completely, or replace the task with one that has no such hazard. Instead of unloading a lorry of heavy gravel bags by hand, lift the bags off with a crane, which removes the manual handling.

2. Reduce the hazard

The next choice is to make the hazard smaller. Carry one or two reams of copier paper instead of a box of five. Replace a hazard with a less hazardous one: since road travel is riskier than rail travel, encourage staff to take the train for business trips where practical. If the car is still needed, use vehicles that meet high safety standards, with drivers who are competent, properly insured and perhaps trained on an approved defensive driving course.

3. Keep people away from the hazard

These controls stop people from coming into contact with the hazard.

• Distance. Store hazardous chemicals in a remote place. Keep people away from noisy machines. Use automated processes. Distance usually keeps most people away most of the time, but people may come close on purpose, for example to fetch chemicals from the store, or by accident, such as contractors, visitors and trespassers who do not know the hazard is there.
• Enclosure. Put guards around the dangerous parts of machinery. Barriers sometimes have to be removed for good reasons such as cleaning or maintenance, but that also means they can be removed without a good reason. Link the guard to the machine's power supply so that the machine cannot run when the guard is off. Other examples are an enclosure around a noisy machine and a spray booth for all painting.

4. Safe systems of work

Safe systems of work include safe work procedures, permits to work and safety rules. They set out how an activity must be done to keep the risk low. People follow them more reliably when they understand why the method matters. For example, rotating two or three people on a noisy job limits each person's exposure, but only if everybody keeps to the time limit and rotates as planned.

5. Personal protective equipment

Goggles, respiratory protection, gloves and hard hats protect a person who comes into contact with the hazard. PPE should not be the first choice, except in special cases such as an emergency, because it always depends on people using it correctly. Provide adequate safety signs where a significant risk remains that cannot be avoided or controlled in any other way.

A study aid, not published or endorsed by IOSH or OSHA. Laws and limits differ between countries.