Preventing Common Household Accidents—Swiss Cheese Model

There was a recent account in the news about the story of three fishermen who survived 9 months adrift at sea in a 29 foot boat. (NYTimes 8/26/06 A3). Although the emphasis of the report was on their survival activities, a review of the events leading to this accident can be helpful in preventing accidents at home.

Background–The boat and crew were on a shark-fishing trip, which typically lasts from 3 days to a week. There was concern at the outset that enough provisions (food, water, fuel) had been laid in for the trip. At sea, the crew lost their shark-fishing tackle. During the search for the equipment, they ran out of fuel. Winds pushed them out to sea where a current caught them and carried the boat 5000 miles west from Mexico to the Marshall Islands. There, the survivors were rescued by a fishing boat.

It was a series of breakdowns or coincidences that finally enabled the accident to occur. In this case, there were insufficient resources, a boat without a radio, poor judgment during the search, and an unfavorable wind and current direction.

Many accidents follow this pattern of several breakdowns. These breakdowns represent holes in the defense against an accident. The pattern is often recognized after the fact. However, a straightforward method of analysis exists that helps to identify the potential areas of risk for an accident before the event occurs.

The model developed by Reason (1990) is based on the assumption that there are several different elements that must all be considered in order have a safe event. Although there is always emphasis on the failure event itself, there are preconditions that have allowed this event to occur. The trick is to analyze these preconditions in advance. The categories are the unsafe act or accident itself, the conditions that enabled the accident event, the supervision, and the influence or attitude of those in charge.

The diagram above illustrates the “Swiss Cheese” name. Each of the levels of defense can have holes in them. Since there are several layers of protection, a failure in any one level does not lead to an accident. However, if all of the breakdowns in defense happen to line up, as with the holes in the diagram above, an accident can occur.

In the above example of the boat adrift, the facts can be classified in 4 defense categories:

Defense Category……………………………… Examples of Hole in Defense

1. Unsafe Act…………………………………..Running out of fuel

2. Precondition for Unsafe Act………..Inadequate Resources/Equipment

3. Unsafe Supervision…………………….Failure to call off search for tackle

4. Organization Influence………………Low regard for safety (lack of funds)

Application for Common Household Accident Prevention–Well, most people do not appear to be in such hazardous situations as the fishermen. Actually though, there are close to 30,000 deaths a year due to household accidents. The National Safety Council also estimates there is a disabling injury every 4 seconds. The magnitude of these numbers is astounding! Since the accidents are spread out both in time and over the country, the size does not attract attention. If they occurred in one place, it would be a disaster. This is a lot of suffering caused by everyday activities. It’s clear that some of it is preventable. The responsibility is with the individuals in their own home.The list of the leading categories is what might be expected:

Burns………. Choking……….. Cuts………. Falls…….. Poisoning

There are many web sites to get specific TIPS of preventive actions to take to reduce the risks of accidents in each category. Obviously, they should be used.

Beyond that, everyone’s situation is a little different; some risks are more specific to your own situation. Reason’s “Swiss Cheese Model” can be used to analyze and address these specific hazards before they become accidents.As an example, take the category of falls. The statistics show that consequences from falls are a serious problem for all ages, especially very young children and older adults.
One way to get started is to begin with a category and consider what one or two areas in your own home make you the most uneasy. It may be a steep set of stairs going into the basement. Then, a hazard assessment can be done by first considering the different preconditions that can lead to falling down the basement stairs. This assessment is followed by the taking into consideration the effects of supervision and attitudes. A typical assessment is shown in the table below:

Defense Categories:

1. Accident/Unsafe Act: Fall down stairs

2. Preconditions . . . . . . . . . . . . . . . .3.Supervision/4.Owner

a) Material stored on stairs.. . . . . . .Allowed to remain (3. Supervision)

b) Dimly lit. . . . . . . . . . . . . . . . . .. . . Tolerated (4. Owner attitude)

c) Not full hand rail. . . . . . . . . . . . . . Tolerated (4. Owner attitude)

d) Slippery walking surface. . . . . . . Tolerated (4. Owner attitude)

e) Door left open. . . . . . . . . . . . . . . Allowed to remain (3. Supervision)

Eliminating the preconditions of the accident is the first level of defense. Some of these preconditions, such as the material stored on the edge of the stairs, can be addressed by better supervision. This increased supervision adds another layer of defense. Others, such as the dim light or the handrail can be corrected by the owners. Some, such as the steepness of the stairs, must be accepted. However, changes in the attitude of the owners to make improvements also adds a layer of defense. Actions at each of these different defense levels, reduce the overall risk of an injury due to a fall.

In every home, look for specific areas that cause the people more concern for safety. People who live there know them. In addition to following good general preventive measures, available on the web, this method allows focus on those topics in a systematic way in order to reduce the risk as much as possible.

However, just doing the exercise, increases the awareness for the risks of accidents in other areas throughout the house. That is another significant benefit.

(diagram credit:

Companion Story to Illustrate:  Cause of  Common Accidents


4 Responses to Preventing Common Household Accidents—Swiss Cheese Model

  1. james lebron says:

    galing ha!!!!!!!!!!!!!!!!!!!!!

  2. […] A more technical description is in the short article: Preventing Common Household Accidents […]

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