What is confined space?
NIOSH (National Institute for Occupational Safety and Health) defines confined space as "a space which by design has limited openings for entry or exit; unfavorable natural ventilation which could contain or produce dangerous air contaminates and which is not intended for continuous employee occupancy."
What are the dangers associated with confined space entry?
Confined space entry can become a very dangerous and costly experience if one is not thoroughly trained on the associated hazards of this responsibility. Common concerns are: elevated noise levels, heat and cold stress, mechanical and electrical hazards, dust, engulfment potential and of primary concern - atmospheric conditions. Generally, these locations have limited entry and egress and are not conductive to prolonged human occupancy without the use of proper procedures and safety equipment.
What are the most common atmospheric conditions I should be concerned about?
Gases typically monitored in confined spaces reside in three categories: oxygen, combustibles and toxic gases. Alarm levels are 19.5% for oxygen deficiency, 23.5% for oxygen enrichment and 10% LEL for combustionable gases. The normal volume of oxygen in ambient air is 20.9%. The two most commonly monitored toxic gases are carbon monoxide and hydrogen sulfide. Carbon monoxide is a by-product of inefficient combustion and hydrogen sulfide is naturally generated from the decomposition of organic materials like grass, wood and dead animal carcasses.
Who should determine which gases to monitor in a confined space?
Determination of which gases to monitor in a confined space is typically the responsibility of a Safety Specialist or a Certified Industrial Hygienist.
Look out for confined spaces - they're not all easy to identify!
Manholes, sewers, boilers, silos, vessels, vat, pipelines, tunnels, storage tanks, chip compartments and underground vaults are identifiable and non-identifiable areas and can be classified as confined spaces. Open-topped water and degreaser tanks, open pits and enclosures with bottom access are also defined as confined spaces. All prohibit natural ventilation, are a potential source of gas generation and can keep gases from escaping, causing a potentially hazardous atmosphere. These areas should be properly labeled and treated with caution. Confined space gas monitors can be hand-held, portable or attached to clothing as personal monitoring devices.
