WHY DO CONFINED SPACES NEED TO BE VENTILATED?

WHAT IS A CONFINED SPACE?

A confined space is a totally or partially closed volume (building, work, equipment, installation, etc.) which:

• has not been designed and built to be permanently occupied by people, nor intended to be, but which, on occasion, may be occupied temporarily to carry out maintenance, servicing, cleaning, punctual and more or less frequent, or unscheduled operations following exceptional events,
• and within which the atmosphere may pose risks to the health and safety of persons entering it due to:
  • either the design or the location of the work,
  • either insufficient natural ventilation,
  • either materials, substances or fluids that it contains or that are used there,
  • either the equipment used there,
  • or the nature of the work carried out there.

     

WHAT ARE THE SECTORS MOST CONCERNED BY CONFINED SPACE WORK?
 

Chemical industry: all types of tanks, cisterns, reactors… having contained toxic, corrosive, flammable, explosive products Food industry: tanks, cellars or cold rooms that have been inerted with nitrogen (presence of gases such as CO₂, SO₂) Transport: road or rail tanks, barges, ships, planes, etc. Sanitation: tanks, sewers or collectors for cleaning, degassing and decontamination operations Agricultural: silo, wells, pits Welding: work on metal enclosures that have contained flammable materials or inside insufficiently ventilated spaces Here are some examples of confined spaces: Wells and pits, Pipes, sewers, collectors that can be visited, Lifting stations, screening stations, Chlorination stations, ozonation in water treatment, Long and narrow galleries, Cisterns, reservoirs, vats, Sludge treatment or storage rooms, Silos, Crawl spaces, cellars,

WHY IS A CONFINED SPACE DANGEROUS? AND WHAT ARE THE MAIN RISKS?

In addition to the general risks, work in confined spaces exposes firefighters to three types of risk:

• suffocation
• poisoning
• fire and explosion

There are several reasons for reduced oxygen levels in a confined space:

• Oxygen consumption, 
• use of an inert gas or 
• gas emission from a natural source.

The majority of accidents which occur during operations in confined spaces, often serious or even fatal, is linked to an oxygen-deficient atmosphere, the presence of toxic smoke or gas or even an explosion or fire. These are the main risks to evaluate when preparing a working procedure.

Confined spaces are dangerous because they have an atmosphere which is not easy to refresh. Any activity or process generating toxic substances or consuming oxygen in a confined space will very quickly increase the risks linked to these substances or the reduced oxygen levels.

In addition, the exposed person cannot generally evacuate quickly if they experience difficulties, as these spaces can be difficult to access, or have travel problems. Also, we must be aware that there is often a problem linked to the difficulty of rescuing or evacuating a victim, particularly if: 

• the access route is restricted
• or the site topography is difficult (low height, narrow),
• if there is poor lighting,
• if the site is cluttered... 

However the speed of a rescue is vital when there is neurotoxicity, acute respiratory distress syndrome, heart failure, etc.

Specific attention must therefore be paid to preparing a rescue and response plan in the event of an accident.

HOW CAN VENTILATION PURIFY A CONFINED SPACE?
 

It is possible to combat the causes of oxygen deficiency with ventilation techniques: extraction when the source of contamination is located: Extracting bad air directly as close as possible to this source, dilution when the source of contamination has spread: Preferably extraction if a small volume, blowing if a larger volume. By blowing directly or via blowing ducts, LEADER fans can: provide fresh air cool an area push toxic gas or smoke outside pressurise a volume to avoid the spread of smoke or gas By suction using dedicated accessories (ventilation ducts and extraction/blow kits), the LEADER range of electric fans can extract toxic gases or smoke where the blowing technique is not suitable.

WHAT ARE THE VENTILATION RECOMMENDATIONS FOR CONFINED SPACES?
 

• Operators must be placed in a fresh air current. It is often useful to introduce air by creating a supply nearby. This supply dilutes the contaminants created by the operations in the area. That is why, if the operation itself is contaminating, it can be beneficial to extract contaminants as close as possible and introduce air, either artificially through an upstream supply, or naturally through openings.

• The fan air inlet will be located in a zone outside any contamination, particularly opposite the wind and far from the contaminated air outlet from the confined space, as well as exhaust gases from petrol-driven motors used for the operation, which must be placed in the open air.

   

• For very large areas, it can be useful to have air mixers inside the room to help dilute and help sweep blind spots.