man entering confined space

4 CONFINED SPACE HAZARDS | TRAINING TUESDAY

Welcome to Training Tuesday! This week, the focus is on confined space hazards and the top 5 hazards you should know about before you enter, exit, or just work around them.  

This article will cover

  • How to define a confined space 
  • 4 specific confined space hazards 
  • What needs to happen before you enter a confined space 

We’ve covered what a confined space is on the blog before—But what specific hazards should you be on the lookout for?

Confined spaces pose hazards by their very definition—The Canadian Occupational Safety and Health Regulations define a confined space as ‘a partially or enclosed space, that may become hazardous to an employee who enters it due to’: 

  • Its design, construction, location or atmosphere 
  • The materials or substances in it, or
  • Any other conditions relating to it. 

4 CONFINED SPACE HAZARDS

When investigating accidents that occur in confined spaces, reports show they occur because worker’s aren’t well-trained or informed on the potential hazards when they enter confined spaces.

Oxygen deficiency causes about 50% of confined space deaths, and often, no testing is done before these accidents. Over 50% of confined space deaths are from rescue attempts by other workers. 

Four specific hazards workers face in confined spaces are: 

  1. Oxygen deficiency and oxygen enrichment
  2. Fire and/or explosion
  3. Toxicity
  4. Drowning in liquids and/or entrapment in free-flowing solids. 

Why are these things so hazardous in confined spaces? Read on to find out. 

CONFINED SPACE HAZARDS | OXYGEN DEFICIENCY—AND THE OPPOSITE

Lack of oxygen is the first hazard facing workers who must enter a confined space. Before entry (and if your risk assessment calls for it) you must test the space for oxygen with an oxygen monitor. You may also need to test the air while you work in the space.

Oxygen deficiency is caused by:

  1. Gases like nitrogen that displace flammable gases   
  2. Oxygen is taken by: 
  • Combustion of flammable substances, like in-welding and other ‘hot work’ 
  • Explosions or fires (Oxygen levels can be dangerously low after a fire is out, since oxygen replaces the products of combustion) 
  • Chemical reactions like metal rust
  • People who work in the space and use available oxygen as they breathe 

Normal air has 21% oxygen by volume—These are the effects of reduced oxygen levels: 

  • 16% Oxygen: Judgement and breathing become impaired—You become quickly exhausted
  • 12% Oxygen: Worker becomes unconscious, and will die unless taken to fresh air
  • 6% Oxygen: Breathing difficulty—This level of oxygen is fatal immediately 

OXYGEN ENRICHMENT—THE OPPOSITE

Too much oxygen is just as bad as not enough oxygen. An oxygen-enriched atmosphere has more than 23% oxygen by volume. 

What’s the risk of too much oxygen? Flammable materials like clothing and hair will burn immediately. Do not use pure oxygen to ventilate a confined space—This is a fire and explosion hazard.  

CONFINED SPACE HAZARDS FIRE AND EXPLOSION

Combustible gases have an explosive range with a lower explosive limit (LEL), and an upper explosive limit (UEL). If the fuel and air mixture is below the LEL or over the UEL, ignition won’t take place—Gas is combustible between its LEL or UEL. 

What else contributes to explosions or fires?

  • Chemicals
  • Poor ventilation 
  • Static electricity 
  • Machinery 

WHAT’S HOT WORK? 

Hot work is considered work that can produce an ignition. It’s important to 

Hot work can be:

  • Welding
  • Cutting
  • Grinding
  • Work with non-explosion proof electrical equipment 

Before you perform hot work in a confined space, you should:

  • Purge/ventilate the area to reduce combustible concentration of airborne dust or mist to a safe level 
  • If ventilation or purging can’t reduce combustible dust, the space must be made inert—This is done by adding an inert gas to alter oxygen levels. The space must be monitored continuously to make sure the atmosphere stays inert. 
  • Wear proper respiratory personal protective equipment, and have the right gear on-hand to rescue or let nearby personnel enter (Like we mention, over 50% of confined space deaths happen to people who try to rescue others, so this is very important). 
  • Make sure the space is purged and consistently ventilated to maintain an atmosphere of less than 5% the LEL
  • Make sure the space is purged and consistently ventilated to maintain an oxygen concentration under 23% 
  • Continuously monitor atmosphere levels in the space
  • Have an entry permit that includes provisions for hot work and includes the appropriate measures to take. 

CONFINED SPACE HAZARDS TOXICITY

There are two huge risks posed by toxic gas in confined spaces. 

  • Chemical asphyxiation 
  • Irritation to respiratory system, skin or eyes 

Especially harmful toxic gases include: 

  • Hydrogen sulphide (H2S): Hydrogen sulphide is a by-product of sewage treatment, petroleum and other industrial processes. Hydrogen sulphide is particularly dangerous as it has a noticeable smell in small concentrations, but hydrogen sulphide gas takes away your sense of smell too, which can make a worker think they’re safe or the smell has dissipated, when in reality, it still lurks. It’s important to note that hydrogen sulphide collects in low areas since it’s heavier than air. 
  • Methane (CH4): Highly explosive. Methane is a by-product of sewage that leaks from gas lines, and can be found in coal mines. Methane displaces oxygen, which can smother workers.  
  • Sulphur dioxide (SO2): Colourless with a strong smell, sulphur dioxide is poisonous in small amounts. 
  • Carbon monoxide (CO): Colourless, odourless, tasteless and fatal in very small concentrations. It comes from incomplete combustion. Being overexposed to carbon monoxide can cause ears to ring, nausea, headache and sleepiness. 

TEST CAREFULLY FOR TOXICITY BEFORE PERSONNEL ENTERS A CONFINED SPACE.

CONFINED SPACE HAZARDS | DROWNING IN LIQUIDS AND/OR ENTRAPMENT IN FREE-FLOWING SOLIDS 

This one is pretty self-explanatory, but in confined spaces where liquids or flowing solids are present (and they often are) there’s always risk of these substances drowning, suffocation, burns or other injuries.

Some of these substances include: 

  • Water (in a tank, for example) 
  • Grain (in a silo) 
  • Materials, like soil, that fall into an excavation or trench 

AVOID CONFINED SPACE HAZARDS—DO THIS BEFORE YOU ENTER: 

Before a worker enters a confined space, these steps must be followed: 

1) Identify the confined space 
2) A plan for entry and work is in place
3) Training is given to all employees who work in or near the space
4) Entrant training
5) Attendant training
6) Training in the use of Personal Protective Equipment
7) Provide the PPE
8) Air Monitoring Protocols, which include possible purging or inerting of the space and then ventilation

GOOD RULE TO FOLLOW: IF YOU CAN’T TEST, IF YOU CAN’T VENTILATE, IF YOU DON’T HAVE BREATHING APPARATUS, IF YOU DON’T HAVE AN ENTRY PROCEDURE DON’T GO IN. 


VISIT OUR BLOG FOR RELATED READING:

CONFINED SPACES: HERCULES’ SAFETY TIPS

STUCK IN A TIGHT SPOT? WHAT TO KNOW IN A CONFINED SPACE

CONFINED SPACE: RESCUE & RETRIEVAL—3M GUEST BLOG


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