Alternatives to the hierarchy of hazard controls

Alternatives to the hierarchy of hazard controls

The traditional wisdom when developing hazard controls is to use the Hierarchy of Controls. The author’s experience is that a better result will be achieved by using either Haddon’s 10 Countermeasures or the A.C.I.R.L. 9 Box Model. The main advantage of these approaches is that it expands your options for control

Hazard Control Model

Various hazard control strategies and models have been developed by safety professionals over the years. One of the most effective but still easiest to apply is that devised by American researcher Bill Haddon

Haddon’s model for hazard control is as follows:

Countermeasure 1 Prevent the marshalling of the form of energy in the first place.

eg. Ripping seams – instead of blasting, substitution of radiation bin level sources with ultra-sonic level detectors, using water based cleaners rather than flammable solvents.

Countermeasure 2 Reduce the amount of energy marshalled.

eg. Radiation – gauge source strength, explosive store licence requirements, control number of gas cylinders in an area

Countermeasure 3 Prevent the release of the energy.

eg. handrails on work stations, isolating procedures, most interlock systems

Countermeasure 4 Modifying the rate or distribution of energy when it is released.

eg. slope of ramps, frangible plugs in gas bottles, seat belts.

Countermeasure 5 Separate in space or time the energy being released from the susceptible person or structure.

eg. minimum heights for powerlines, divided roads, blasting fuse.

Countermeasure 6 Interpose a material barrier to stop energy or to attentuate to acceptable levels.

eg. electrical insulation, personal protective equipment, machinery guards, crash barriers

Countermeasure 7 Modify the contact surface by rounding or softening to minimise damage when energy contacts susceptible body.

eg. round edges on furniture, building bumper bars, padded dashboards in cars.

Countermeasure 8 Strengthen the structure living or non-living that would otherwise be damaged by the energy exchange.

eg. earthquake and fire resistant buildings, weightlifting.

Countermeasure 9 To move rapidly to detect and evaluate damage and to counter its continuation and extension.

eg. sprinkler systems, emergency medical care, alarm systems of many types.

Countermeasure 10 Stabilisation of damage – long term rehabilitative and repair measure.

eg. clean-up procedures, spill disposal, physiotherapy


Generally the larger the amounts of energy involved in relation to the resistance of the structures at risk, the earlier in the countermeasure sequence must the strategy be selected. In many situations where preventative measures are being considered the application of more than one countermeasure may be appropriate.

Countermeasures may be ‘passive’ in that they require no action on the part of persons, or ‘active in the sense that they require some action or co-operation on the part of the persons, perhaps in association with a design related countermeasure (eg. seatbelts).

Passive’ countermeasures tend to be more reliable in the long term. A short term solution to an immediate problem may require the adoption of an ‘active’ countermeasure eg. toolbox sessions on replacing guards over a mechanical hazard, the long term or ‘passive’ countermeasure might be the fitting of interlocks to the guard so that power is off when the guard is off.

Further reading


Haddon, W ‘On the escape of tigers an ecologic note – strategy options in reducing losses in energy damaged people and property’ Technology Review Massachusetts Institute of Technology, 72;7, 44-53, 1970.

A.C.I.R.L. 9 Box Model

This model says that to have effective control one must have at least one control in each of the boxes. Experience in industry suggests many organizations have many Prevention controls and many Contingency controls (nice trucks with flashing red lights, first-aid kits, trained first-aiders etc) but that they are poor at Monitoring the effectiveness of these controls





Equipment / Engineering

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