OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 5 Confined Spaces

Section 45 Hazard assessment

Restricted spaces have a limited means of entry and exit. Entry points may not be designed for easy walk in. Other limitations include access by ladders or by stairways that provide poor access because of steep slope, narrow width or extreme length. Physical obstructions such as bulkheads, collapsed material, or machinery may impede exit. Limited means of entry and exit can make escape or rescue difficult.

A “restricted space” is an enclosed or partially enclosed space, not intended for continuous human occupancy that has a restricted, limited or impeded means of entry or exit because of its construction. It can be thought of as a work area in which the only hazard is the difficulty of getting into or out of the space. All other hazards are either non-existent or have been eliminated or controlled as required by Part 2. Restricted spaces are therefore not subject to the permitting, atmosphere testing and tending worker requirements of a confined space. Employers and workers must be mindful that a restricted space can become a confined space if conditions or work practices change. Employers who voluntarily apply relevant sections of ANSI Z117.1-2003, Safety Requirements for Confined Spaces, might refer to restricted spaces as “non-permitted confined spaces”.

Examples of a restricted space include

(a) an electrical or communication utility vault,
(b) a building crawl space,
(c) a trench with a temporary protective structure, and
(d) a deep excavation requiring ladder or lift access.

Despite being classified as a restricted space, the following requirements of Part 5 continue to apply to workers entering a restricted space:

  • a hazard assessment must be performed prior to entry – section 45;
  • workers assigned duties related to the entry must be trained to recognize hazards and how to perform their duties in a safe and healthy manner – section 46;
  • general safety requirements involving the use and availability of safety, personal protective, and emergency equipment, as well as a communication system – section 48;
  • prevention of unauthorized persons entering a restricted space – section 50;
  • protection of workers from hazards created by traffic in the area of the restricted space – section 51;
  • workers cannot enter or remain in a restricted space unless an effective rescue can be carried out – section 55;
  • a competent worker, designated by the employer, must be in communication with the worker(s) inside a restricted space – section 56; and
  • a safe means of entry and exit must be available to all workers required to work in the restricted space – section 57.

If a worker enters a confined or restricted space to work, the employer must appoint a competent person to carry out the tasks listed in this section. The competent person must be knowledgeable about confined or restricted spaces and capable of carrying out each of the listed activities.

Figure 5.1 shows a flowchart that helps to determine if the space is a confined space or a restricted space.

Figure 5.1 Flowchart to determine type of space

In assessing the hazards that workers are likely to be exposed to, the requirements of Part 2 of the OHS Code – Hazard Assessment, Elimination and Control – must be
met. The hazard assessment needs to be revised whenever there is evidence to indicate that it is no longer valid and when any of the conditions listed in subsection 7(4) of the OHS Code is met.

Some of the hazards of confined spaces include:

(a) oxygen deficient atmospheres – can cause brain damage and death. Oxygen deficiency can be caused by rusting (or oxidation) of a steel vessel, any form of burning, including welding or brazing, absorption by grain or soils, consumption by bacteria that can use up some or all of the oxygen in the space;

(b) asphyxiant gas – physiologically inert gases can dilute or displace atmospheric oxygen below the level required for normal human functioning. Common examples of asphyxiant gases are carbon dioxide, ethane, helium, hydrogen, methane and nitrogen. During a process known as purging, an inert gas such as nitrogen is deliberately pumped into a confined space to purge or force out flammable or explosive atmospheres from a confined space. The inert gas is usually replaced with fresh air before the space is safe to enter;

(c) toxic atmospheres – containing gases, vapours, dusts or fumes that have poisonous effects on the body. Cleaning, painting or welding may produce dangerous vapours or fumes. Gases such as hydrogen sulphide may leak into the space from gas pockets underground. Carbon monoxide may be generated in the space by an internal combustion engine. Methane may be created through the fermentation of plant material in the space;

(d) flammable or explosive atmospheres – containing flammable gases, vapours or dusts that could be ignited by a spark or open flame. The risk of explosion increases if an oxygen-enriched atmosphere is present i.e. if the oxygen content is greater than 23 percent by volume;

(e) engulfment – workers can be trapped or buried by dry bulk materials such as grain, sand, flour, fertilizer and sawdust;

(f) operation of moving parts – being trapped or crushed by augers, mixers, agitators, conveyor belts, etc. This equipment must be locked out before anyone enters the confined space;

(g) uncontrolled introduction ofsteam, water or other gas or liquid;

(h) other hazards – these could result from the work being done e.g. noise, extremes of temperature, radiation, manual handling and falls.