Falls from elevations are severe accidents that occur in many industries and occupations. Falls from elevations result in injuries which are produced by contact between the falling person and the source of injury, under the following circumstances:

• The motion of the person and the force of impact are generated by gravity.
• The point of contact with the source of injury is lower than the surface supporting the person at the start of the fall.

From this definition, it may be surmised that falls are unavoidable because gravity is always present. Falls are accidents, somehow predictable, occurring in all industrial sectors and occupations and having a high severity. Strategies to reduce the number of falls, or at least reduce the severity of the injuries if falls occur, are discussed in this article.

The Height of the Fall

The severity of injuries caused by falls is intrinsically related to the height of fall. But this is only partly true: the free-fall energy is the product of the falling mass times the height of the fall, and the severity of the injuries is directly proportional to the energy transferred during the impact. Statistics of fall accidents confirm this strong relationship, but show also that falls from a height of less than 3 m can be fatal. A detailed study of fatal falls in construction shows that 10% of the fatalities caused by falls occurred from a height less than 3 m (see figure 1). Two questions are to be discussed: the 3-m legal limit, and where and how a given fall was arrested.

Figure 1. Fatalities caused by falls and the height of fall in the US construction industry, 1985-1993

In many countries, regulations make fall protection mandatory when the worker is exposed to a fall of more than 3 m. The simplistic interpretation is that falls of less than 3 m are not dangerous. The 3-m limit is in fact the result of a social, political and practical consensus which says it is not mandatory to be protected against falls while working at the height of a single floor. Even if the 3-m legal limit for mandatory fall protection exists, fall protection should always be considered. The height of fall is not the sole factor explaining the severity of fall accidents and the fatalities due to falls; where and how the person falling came to rest must also be considered. This leads to analysis of the industrial sectors with higher incidence of falls from elevations.

Where Falls Occur

Falls from elevations are frequently associated with the construction industry because they account for a high percentage of all fatalities. For example, in the United States, 33% of all fatalities in construction are caused by falls from elevations; in the UK, the figure is 52%. Falls from elevations also occur in other industrial sectors. Mining and the manufacturing of transportation equipment have a high rate of falls from elevations. In Quebec, where many mines are steep, narrow-vein, underground mines, 20% of all accidents are falls from elevations. The manufacture, use and maintenance of transportation equipment such as airplanes, trucks and railroad cars are activities with a high rate of fall accidents (table 1). The ratio will vary from country to country depending on the level of industrialization, the climate, and so on; but falls from elevations do occur in all sectors with similar consequences.

Table 1. Falls from elevations: Quebec 1982-1987

                               Falls from elevations                         Falls from elevations in all accidents
                               per 1,000 workers

Construction                        14.9                                                10.1%

Heavy industry                      7.1                                                  3.6%

Having taken into consideration the height of fall, the next important issue is how the fall is arrested. Falling into hot liquids, electrified rails or into a rock crusher could be fatal even if the height of fall is less than 3 m.

Causes of Falls

So far it has been shown that falls occur in all economic sectors, even if the height is less than 3 m. But why do humans fall? There are many human factors which can be involved in falling. A broad grouping of factors is both conceptually simple and useful in practice:

Opportunities to fall are determined by environmental factors and result in the most common type of fall, namely the tripping or slipping that result in falls from grade level. Other falling opportunities are related to activities above grade.

Liabilities to fall are one or more of the many acute and chronic diseases. The specific diseases associated with falling usually affect the nervous system, the circulatory system, the musculoskeletal system or a combination of these systems.

Tendencies to fall arise from the universal, intrinsic deteriorative changes that characterize normal ageing or senescence. In falling, the ability to maintain upright posture or postural stability is the function that fails as a result of combined tendencies, liabilities and opportunities.

Postural Stability

Falls are caused by the failure of postural stability to maintain a person in an upright position. Postural stability is a system consisting of many rapid adjustments to external, perturbing forces, especially gravity. These adjustments are largely reflex actions, subserved by a large number of reflex arcs, each with its sensory input, internal integrative connections, and motor output. Sensory inputs are: vision, the inner ear mechanisms that detect position in space, the somatosensory apparatus that detects pressure stimuli on the skin, and the position of the weight-bearing joints. It appears that visual perception plays a particularly important role. Very little is known about the normal, integrative structures and functions of the spinal cord or the brain. The motor output component of the reflex arc is muscular reaction.

Vision

The most important sensory input is vision. Two visual functions are related to postural stability and control of gait:

• the perception of what is vertical and what is horizontal is basic to spatial orientation
• the ability to detect and discriminate objects in cluttered environments.

Two other visual functions are important:

• the ability to stabilize the direction in which the eyes are pointed so as to stabilize the surrounding world while we are moving and immobilize a visual reference point
• the ability to fixate and pursue definite objects within the large field (“keep an eye on”); this function requires considerable attention and results in deterioration in the performance of any other simultaneous, attention-demanding tasks.

Causes of postural instability

The three sensory inputs are interactive and interrelated. The absence of one input—and/or the existence of false inputs—results in postural instability and even in falls. What could cause instability?

Vision

• the absence of vertical and horizontal references—for example, the connector at the top of a building
• the absence of stable visual references—for example, moving water under a bridge and moving clouds are not stable references
• the fixing a definite object for work purposes, which diminishes other visual functions, such as the ability to detect and discriminate objects that can cause tripping in a cluttered environment
• a moving object in a moving background or reference—for example, a structural steel component moved by a crane, with moving clouds as background and visual reference.

Inner ear

• having the person’s head upside down while the level equilibrium system is at its optimum performance horizontally
• travelling in pressurized aircraft
• very fast movement, as, for example, in a roller-coaster
• diseases.

Somatosensory apparatus (pressure stimuli on the skin and position of weight-bearing joints)

• standing on one foot
• numbed limbs from staying in a fixed position for a long period of time—for example, kneeling down
• stiff boots
• very cold limbs.

Motor output

• numbed limbs
• tired muscles
• diseases, injuries
• ageing, permanent or temporary disabilities
• bulky clothing.

Postural stability and gait control are very complex reflexes of the human being. Any perturbations of the inputs may cause falls. All perturbations described in this section are common in the workplace. Therefore, falling is somehow natural and prevention must therefore prevail.

Strategy for Fall Protection

As previously noted, the risks of falls are identifiable. Therefore, falls are preventable. Figure 2 shows a very common situation where a gauge must be read. The first illustration shows a traditional situation: a manometer is installed at the top of a tank without means of access In the second, the worker improvises a means of access by climbing on several boxes: a hazardous situation. In the third, the worker uses a ladder; this is an improvement. However, the ladder is not permanently fixed to the tank; it is therefore probable that the ladder may be in use elsewhere in the plant when a reading is required. A situation such as this is possible, with fall arrest equipment added to the ladder or the tank and with the worker wearing a full body harness and using a lanyard attached to an anchor. The fall-from-elevation hazard still exists.

Figure 2. Installations for reading a gauge

In the fourth illustration, an improved means of access is provided using a stairway, a platform and guardrails; the benefits are a reduction in the risk of falling and an increase in the ease of reading (comfort), thus reducing the duration of each reading and providing a stable work posture allowing for a more precise reading.

The correct solution is illustrated in the last illustration. During the design stage of the facilities, maintenance and operation activities were recognized. The gauge was installed so that it could be read at ground level. No falls from elevations are possible: therefore, the hazard is eliminated.

This strategy puts the emphasis on the prevention of falls by using the proper means of access (e.g., scaffolds, ladders, stairways) (Bouchard 1991). If the fall cannot be prevented, fall arrest systems must be used (figure 3). To be effective, fall arrest systems must be planned. The anchorage point is a key factor and must be pre-engineered. Fall arrest systems must be efficient, reliable and comfortable; two examples are given in Arteau, Lan and Corbeil (to be published) and Lan, Arteau and Corbeil (to be published). Examples of typical fall prevention and fall arrest systems are given in table 2. Fall arrest systems and components are detailed in Sulowski 1991.

Figure 3. Fall prevention strategy

Table 2. Typical fall prevention and fall arrest systems

The emphasis on prevention is not an ideological choice, but rather a practical choice. Table 3 shows the differences between fall prevention and fall arrest, the traditional PPE solution.

Table 3. Differences between fall prevention and fall arrest

For the employer and the designer, it is easier to build fall prevention systems because their minimum breaking strength requirements are 10 to 20 times less than those of fall arrest systems. For example, the minimum breaking strength requirement of a guard rail is around 1 kN, the weight of a large man, and the minimum breaking strength requirement of the anchorage point of an individual fall arrest system could be 20 kN, the weight of two small cars or 1 cubic metre of concrete. With prevention, the fall does not occur, so the risk of injury does not exist. With fall arrest, the fall does occur and even if arrested, a residual risk of injury exists.

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Confined spaces are ubiquitous throughout industry as recurring sites of both fatal and nonfatal accidents. The term confined space traditionally has been used to label particular structures, such as tanks, vessels, pits, sewers, hoppers and so on. However, a definition based on description in this manner is overly restrictive and defies ready extrapolation to structures in which accidents have occurred. Potentially any structure in which people work could be or could become a confined space. Confined spaces can be very large or they can be very small. What the term actually describes is an environment in which a broad range of hazardous conditions can occur. These condition include personal confinement, as well as structural, process, mechanical, bulk or liquid material, atmospheric, physical, chemical, biological, safety and ergonomic hazards. Many of the conditions produced by these hazards are not unique to confined spaces but are exacerbated by involvement of the boundary surfaces of the confined space.

Confined spaces are considerably more hazardous than normal workspaces. Seemingly minor alterations in conditions can immediately change the status of these workspaces from innocuous to life-threatening. These conditions may be transient and subtle, and therefore are difficult to recognize and to address. Work involving confined spaces generally occurs during construction, inspection, maintenance, modification and rehabilitation. This work is nonroutine, short in duration, nonrepetitive and unpredictable (often occurring during off-shift hours or when the unit is out of service).

Confined Space Accidents

Accidents involving confined spaces differ from accidents that occur in normal workspaces. A seemingly minor error or oversight in preparation of the space, selection or maintenance of equipment or work activity can precipitate an accident. This is because the tolerance for error in these situations is smaller than for normal workplace activity.

The occupations of victims of confined space accidents span the occupational spectrum. While most are workers, as might be expected, victims also include engineering and technical people, supervisors and managers, and emergency response personnel. Safety and industrial hygiene personnel also have been involved in confined space accidents. The only data on accidents in confined spaces are available from the United States, and these cover only fatal accidents (NIOSH 1994). Worldwide, these accidents claim about 200 victims per year in industry, agriculture and the home (Reese and Mills 1986). This is at best a guess based on incomplete data, but it appears to be applicable today. About two-thirds of the accidents resulted from hazardous atmospheric conditions in the confined space. In about 70% of these the hazardous condition existed prior to entry and the start of work. Sometimes these accidents cause multiple fatalities, some of which are the result of the original incident and a subsequent attempt at rescue. The highly stressful conditions under which the rescue attempt occurs often subject the would-be rescuers to considerably greater risk than the initial victim.

The causes and outcomes of accidents involving work external to structures that confine hazardous atmospheres are similar to those occurring inside confined spaces. Explosion or fire involving a confined atmosphere caused about half of the fatal welding and cutting accidents in the United States. About 16% of these accidents involved “empty” 205 l (45 gal UK, 55 gal US) drums or containers (OSHA 1988).

Identification of Confined Spaces

A review of fatal accidents in confined spaces indicates that the best defences against unnecessary encounters are an informed and trained workforce and a programme for hazard recognition and management. Development of skills to enable supervisors and workers to recognize potentially hazardous conditions is also essential. One contributor to this programme is an accurate, up-to-date inventory of confined spaces. This includes type of space, location, characteristics, contents, hazardous conditions and so on. Confined spaces in many circumstances defy being inventoried because their number and type are constantly changing. On the other hand, confined spaces in process operations are readily identifiable, yet remain closed and inaccessible almost all of the time. Under certain conditions, a space may be considered a confined space one day and would not be considered a confined space the next.

A benefit from identifying confined spaces is the opportunity to label them. A label can enable workers to relate the term confined space to equipment and structures at their work location. The downside to the labelling process includes: (1) the label could disappear into a landscape filled with other warning labels; (2) organizations that have many confined spaces could experience great difficulty in labelling them; (3) labelling would produce little benefit in circumstances where the population of confined spaces is dynamic; and (4) reliance on labels for identification causes dependence. Confined spaces could be overlooked.

Hazard Assessment

The most complex and difficult aspect in the confined space process is hazard assessment. Hazard assessment identifies both hazardous and potentially hazardous conditions and assesses the level and acceptability of risk. The difficulty with hazard assessment occurs because many of the hazardous conditions can produce acute or traumatic injury, are difficult to recognize and assess, and often change with changing conditions. Hazard elimination or mitigation during preparation of the space for entry, therefore, is essential for minimizing the risk during work.

Hazard assessment can provide a qualitative estimate of the level of concern attached to a particular situation at a particular moment (table 1). The breadth of concern within each category ranges from minimal to some maximum. Comparison between categories is not appropriate, since the maximum level of concern can differ considerably.

Table 1. Sample form for assessment of hazardous conditions

NA = not applicable. The meanings of certain terms such as toxic substance, oxygen deficiency, oxygen enrichment, mechanical hazard, and so on, require further specification according to standards that exist in a particular jurisdiction.

Each entry in table 1 can be expanded to provide detail about hazardous conditions where concern exists. Detail also can be provided to eliminate categories from further consideration where concern is non-existent.

Fundamental to the success of hazard recognition and assessment is the Qualified Person. The Qualified Person is deemed capable by experience, education and/or specialized training, of anticipating, recognizing and evaluating exposures to hazardous substances or other unsafe conditions and specifying control measures and/or protective actions. That is, the Qualified Person is expected to know what is required in the context of a particular situation involving work within a confined space.

A hazard assessment should be performed for each of the following segments in the operating cycle of the confined space (as appropriate): the undisturbed space, pre-entry preparation, pre-work inspection work activities (McManus, manuscript) and emergency response. Fatal accidents have occurred during each of these segments. The undisturbed space refers to the status quo established between closure following one entry and the start of preparation for the next. Pre-entry preparations are actions taken to render the space safe for entry and work. Pre-work inspection is the initial entry and examination of the space to ensure that it is safe for the start of work. (This practice is required in some jurisdictions.) Work activities are the individual tasks to be performed by entrants. Emergency response is the activity in the event rescue of workers is required, or other emergency occurs. Hazards that remain at the start of work activity or are generated by it dictate the nature of possible accidents for which emergency preparedness and response are required.

Performing the hazard assessment for each segment is essential because the focus changes continuously. For example, the level of concern about a specific condition could disappear following pre-entry preparation; however, the condition could reappear or a new one could develop as a result of an activity which occurs either inside or outside the confined space. For this reason, assessing a level of concern to a hazardous condition for all time based only on an appraisal of pre-opening or even opening conditions would be inappropriate.

Instrumental and other monitoring methods are used for determining the status of some of the physical, chemical and biological agents present in and around the confined space. Monitoring could be required prior to entry, during entry or during work activity. Lockout/tagout and other procedural techniques are used to deactivate energy sources. Isolation using blanks, plugs and caps, and double block and bleed or other valve configurations prevents entry of substances through piping. Ventilation, using fans and eductors, is often necessary to provide a safe environment for working both with and without approved respiratory protection. Assessment and control of other conditions relies on the judgement of the Qualified Person.

The last part of the process is the critical one. The Qualified Person must decide whether the risks associated with entry and work are acceptable. Safety can best be assured through control. If hazardous and potentially hazardous conditions can be controlled, the decision is not difficult to make. The less the level of perceived control, the greater the need for contingencies. The only other alternative is to prohibit the entry.

Entry Control

The traditional methods for managing on-site confined space activity are the entry permit and the on-site Qualified Person. Clear lines of authority, responsibility and accountability between the Qualified Person and entrants, standby personnel, emergency responders and on-site management are required under either system.

The function of an entry document is to inform and to document. Table 2 (below) provides a formal basis for performing the hazard assessment and documenting the results. When edited to include only information relevant to a particular circumstance, this becomes the basis for the entry permit or entry certificate. The entry permit is most effective as a summary that documents actions performed and indicates by exception, the need for further precautionary measures. The entry permit should be issued by a Qualified Person who also has the authority to cancel the permit should conditions change. The issuer of the permit should be independent of the supervisory hierarchy in order to avoid potential pressure to speed the performance of work. The permit specifies procedures to be followed as well as conditions under which entry and work can proceed, and records test results and other information. The signed permit is posted at the entry or portal to the space or as specified by the company or regulatory authority. It remains posted until it is either cancelled, replaced by a new permit or the work is completed. The entry permit becomes a record upon completion of the work and must be retained for recordkeeping according to requirements of the regulatory authority.

The permit system works best where hazardous conditions are known from previous experience and control measures have been tried and proven effective. The permit system enables expert resources to be apportioned in an efficient manner. The limitations of the permit arise where previously unrecognized hazards are present. If the Qualified Person is not readily available, these can remain unaddressed.

The entry certificate provides an alternative mechanism for entry control. This requires an onsite Qualified Person who provides hands-on expertise in the recognition, assessment and evaluation, and control of hazards. An added advantage is the ability to respond to concerns on short notice and to address unanticipated hazards. Some jurisdictions require the Qualified Person to perform a personal visual inspection of the space prior to the start of work. Following evaluation of the space and implementation of control measures, the Qualified Person issues a certificate describing the status of the space and conditions under which the work can proceed (NFPA 1993). This approach is ideally suited to operations that have numerous confined spaces or where conditions or the configuration of spaces can undergo rapid change.

Table 2. A sample entry permit

Department:

Location:

Building/Shop:

Equipment/Space:

Part:

Date:                                                 Assessor:

Duration:                                           Qualification:

Space:

Description:

Contents:

Process:

Atmospheric Hazards

Oxygen Deficiency                       Yes  No  Controlled

Oxygen Enrichment                     Yes  No  Controlled

Chemical                                      Yes  No  Controlled

Substance Concentration            (Acceptable standard:                                )

Biological                                      Yes  No  Controlled

Fire/Explosion                              Yes  No  Controlled

Substance Concentration            (Acceptable maximum:                     % LFL)

Physical Agents

Noise/Vibration                            Yes  No  Controlled

Heat/Cold Stress                         Yes  No  Controlled

Non/Ionizing Radiation                 Yes  No  Controlled

Laser                                            Yes  No  Controlled

Type Level                                    (Acceptable maximum:                              )

Process Hazard
(Refer to procedure.)                   Yes  No  Controlled

Safety Hazards

Engulfment/Immersion
(Refer to corrective action.)          Yes  No  Controlled

Fall
(Refer to corrective action.)          Yes  No  Controlled

Explosive/Implosive
(Refer to corrective action.)           Yes  No  Controlled

4. Work Procedure

Atmospheric Hazard

Oxygen Enrichment                           

(Refer to requirement for additional testing. Record results.
Refer to requirement for protective measures.)                                    

Concentration:                                   Yes  No  Controlled

                                                           (Acceptable maximum:                             %)

Fire/Explosion             

(Refer to requirement for additional testing. Record results. Refer to requirement
for protective measures.)
Substance Concentration                 Yes  No  Controlled

                                                          (Acceptable standard:                                 )

Physical Agents

Heat/Cold Stress           

(Refer to requirement for protective measures. Refer to requirement for
additional testing. Record results.)
Temperature:                                    Yes  No  Controlled

                                                          (Acceptable range:                                      )

Mechanical Hazard
(Refer to requirement for protective measures.)            Yes  No  Controlled

Process Hazard

Safety Hazards

Structural Hazard
(Refer to requirement for protective measures.)            Yes  No  Controlled

Fall
(Refer to requirement for protective measures.)            Yes  No  Controlled

Visibility/light level
(Refer to requirement for protective measures.)            Yes  No  Controlled

Hot/Cold Surfaces
(Refer to requirement for protective measures.)            Yes  No  Controlled

Communications equipment and procedure (specify)

Ventilation (specify)

(Continues on next page)

CONFINED SPACE—ENTRY PERMIT

Specify testing requirements and frequency

Entry Supervisor

Authorized Entrants

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