Western Canada Mine Rescue Manual Chapter 8 PDF

Western Canada Mine Rescue Manual Chapter 8 Respiratory Protective Equipment 8-1 OBJECTIVES Selecting the right protective equipment can mean the difference between life and death when responding to incidents in dangerous environments. Upon completion of this chapter, the trainee shall be able to de...

Western Canada Mine Rescue Manual Chapter 8 Respiratory Protective Equipment 8-1 OBJECTIVES Selecting the right protective equipment can mean the difference between life and death when responding to incidents in dangerous environments. Upon completion of this chapter, the trainee shall be able to demonstrate competency in:  The hazardous respiratory environments encountered in mine rescue work  Breathing apparatus concepts  Limitations and safety features of breathing apparatus  Recharging and hydrostatic testing of compressed gas cylinders Refer to manufacturer’s guidelines and site-specific procedures for a comprehensive overview of care, use, specifications, and handling of breathing apparatus. Introduction People who are exposed to a dangerous atmosphere may not be aware that the danger exists nor of the need to protect themselves. Proper and adequate ventilation is the best solution to a dangerous atmosphere. (An exception to this rule is when fire is involved.) Proper respiratory equipment must be used if a mine rescue team cannot ventilate an area and lives or property are at risk. Oxygen content can reach dangerous levels in hazardous scenarios, such as in:  Incidents involving fire  Confined spaces, including buildings, manholes, tunnels, vaults, chemical tanks, oil tanks, storage bins, silos, equipment, and sumps  Mine workings Hazardous atmospheres:  Toxic gases or vapours  Oxygen deficiency/ asphyxiating gases  Explosive/flammable gases or vapours  Smoke, aerosols, fumes (particulate contaminants) The lungs and respiratory tract are more vulnerable to injury from hazardous atmospheres than any other part of the body. Inhaling heated gases may cause oedema (fluid collection) in the lungs, which can cause death by asphyxiation. If the air is heated or moist, the damage can be much worse. The tissue damage from hot air is not immediately reversible by introducing fresh, cool air. When taken quickly into the lungs, it may cause a serious decrease in blood pressure and failure of the circulatory system. 8-2 APPARATUS CONCEPTS Mine rescue teams use both open‑circuit and closed‑circuit breathing apparatus. In a non-self-contained breathing apparatus, oxygen from the atmosphere is drawn through a filter to the rescuer’s breathing apparatus. In environments in which carbon monoxide is present, there must be adequate oxygen in the atmosphere for a non-self-contained breathing apparatus to function properly. In a self-contained breathing apparatus, breathable air is supplied from a cylinder or released as a product of a chemical reaction that occurs in a component of the apparatus. In an open-circuit apparatus, exhaled air is released into the surrounding atmosphere. In a closed-circuit apparatus, exhaled air is recirculated within the system. Positive Pressure versus Negative Pressure The apparatus will deliver breathable oxygen/air to the wearer under positive pressure. A positive pressure system will maintain an internal pressure higher than the external pressure. The advantages of positive pressure:  Reduces the potential for external atmospheric toxins (smoke, gases) to penetrate into the system, i.e. if the facepiece seal is broken.  No added breathing effort is required by the wearer (unrestricted). A negative pressure system’s internal pressure is lower than the external pressure. All makes and models of breathing apparatuses have manufacturer’s instructions for donning (putting the apparatus on) and doffing (taking the apparatus off). Rescuers must train to the manufacturers’ procedures of the models used on their site. Air-Purifying Respirators (APRs) (non-self-contained, open-circuit) APRs remove contaminants in the air by filtering out particulates (e.g., dusts, fumes, mists), gases, and vapours. They require an adequate amount of oxygen (i.e., 19.5%) in the atmosphere to be used as they do not create or supply oxygen for the wearer. They have a limited protection factor. Cartridge versions are colour-coded for their respective atmospheric contaminant. The masks come in a variety of forms, including (from L-R) disposable, half-face cartridge and full-face cartridge models. Fit tests shall be performed for all mask type respirators. Ensure compliance with local regulations, standards, and legislation. 8-3 SELF-RESCUERS (non-self-contained, open-circuit) MSA W65 This is a respirator strictly designed for self-rescue to protect the wearer against carbon monoxide gas. It is small and easily carried on the underground miner’s belt. The MSA Model W65 is sealed with nitrogen. If the seal is broken, the unit should be removed from service because the chemicals in the apparatus deteriorate. Users should always examine their selfrescuers for damage before use. Operation  Air is drawn in through the bottom of the self-rescuer and passes through the coarse-dust filter bag.  The air then passes through a fine-dust filter in the bottom of the canister.  The air then passes through a drying agent that removes excess moisture that reduces the effectiveness and deteriorates the Hopcalite. The Hopcalite is not consumed in the reaction as it is a catalyst.  The air flows through the Hopcalite, which causes a catalytic reaction changing the carbon monoxide to carbon dioxide, creating heat in the process.  The air, which can be dangerously hot, passes through a heat exchanger to be cooled.  When exhaled, the air again passes through the heat exchanger and out through a check valve, which does not allow air from the outside back into the respirator. The heat exchanger incorporates both the outside atmosphere and exhaled breath to cool the inhaled air. The W65 self-rescuer will:  Require at least 19.5% oxygen in the air  Function in an environment with no more than 95% humidity  Protect the wearer against 1% (10,000 PPM) carbon monoxide for one hour  Generate heat when exposed to higher levels of carbon monoxide, thereby shortening the unit’s duration. Wearers must be in a respirable atmosphere before removing the unit.  Have a service life of 10 years and a shelf life of 15 years when properly stored  Require testing as per manufacturer’s specifications 8-4 Fig 8-1: How a Self-Rescue functions 8-5 SELF-CONTAINED SELF-RESCUERS (SCSR) (Closed Circuit, Self-Contained) Oxygen-generating self-rescuers are designed strictly for self-rescue and to function completely independent of the surrounding atmosphere. Operation  Oxygen is released by the chemical reaction of moisture from the exhaled breath mixing with the potassium superoxide (KO2). This reaction produces heat. A second reaction takes place between the newly created potassium hydroxide and the carbon dioxide from the exhaled breath, which retains/absorbs the carbon dioxide.  The oxygen is inhaled from the breathing bag, which also serves as a breathing air reservoir.  A heat exchanger is built into the breathing tube to cool the air before inhalation.  A quick‑start system covers the immediate oxygen requirements of the user until the chemical of the canister becomes activated. A number of oxygen generating self-rescuers are available on the market today. Some include: From L-R: Drager Oxy 3000/6000, Drager Oxy SR 90 and CSE Self-Rescuer Long Duration 8-6 CLOSED-CIRCUIT BREATHING APPARATUS (CCBA) (Closed circuit, self-contained, positive pressure, re-breather) A CCBA’s main functions are to absorb carbon dioxide and provide oxygen. CCBAs also recycle the unused oxygen from the wearer’s exhaled breath. The recycled air is enriched with oxygen from a compressed oxygen cylinder prior to inhalation. The positive pressure inside the facepiece protects the wearer from a potentially toxic environment. Modern CCBAs maintain positive pressure by using springs on the breathing bag/chamber and a demand valve when the internal volume of oxygen in the system has decreased. The increased duration for the wearer (rated up to four hours) allows CCBAs to be used in incidents at both surface and underground mines. Two common positive pressure CCBAs are:  Dräger – PSS BG4  Bio Marine - BioPak 240R Drager PSS BG4 Bio Marine BioPak 240R 8-7 SELF-CONTAINED BREATHING APPARATUS (SCBA) (Open Circuit, Self-Contained, Positive Pressure) SCBAs protect the wearer from hazardous atmospheres by providing breathable air. Several manufacturers build SCBAs for emergency response and industrial use. There are many models of the control configuration but the basic components and operating principles remain the same. Open-circuit SCBAs use filtered, compressed air. Most open-circuit systems have two regulators: a firststage regulator to reduce the pressure of the compressed air in the cylinder and a second stage regulator to reduce it even further to a level just above atmospheric pressure. This air is then fed to the facepiece via a demand valve which is activated by inhalation. When the wearer exhales, the breath exits the facepiece via the exhalation valve to the outside atmosphere thus making it an open circuit. SCBAs have purge/bypass valves for emergency situations. The four major components of the SCBA are:  Backpack assembly: Designed to hold the air cylinder on the rescuer’s back.  Regulator: Reduces the cylinder pressure to flow and pressure levels required for inhalation.  Facepiece (mask): Designed to deliver low-pressure air from the regulator into the mouth and nose of the rescuer. It may also provide some protection from facial burns and contact of smoke and fire gases with the eyes.  Air cylinder: Designed to store a quantity of breathable air under pressure. Depending on construction and size, cylinders may be rated for 30–90 minutes at pressures between 2,216– 5,500 psi. Drager PSS 7000, Scott Safety Air Pak X3, MSA G1 SCBA Rapid Intervention Crew/Company Universal Air Connections (RIC UACs) allow teams to directly attach two air cylinders of any kind to provide air to SCBAs worn by casualties or other rescuers when their supply is low. It is not for quick charging, buddy-breathing or any other unapproved use. If the unit has a RIC connection, it is a standard fitting that is dedicated for emergency use: the Rapid Intervention Crew/Company Universal Air Connection (RIC UAC), NFPA 1981 (2013 edition). 8-8 Personal Alert Safety System (PASS) A PASS device is used by the wearer of an SCBA as a safety alarm with a high volume siren if the wearer remains motionless, such as when the wearer has collapsed or is trapped (usually set at pre-alarm when motionless; full alarm of motionless for 30 seconds). It can also be triggered manually. The loud noise provides a location for the rescue personnel to follow. NFPA-compliant SCBA models have the PASS system built into the unit. It is activated automatically when the SCBA air is turned on. Some non-built-in models have a key which turns on the device. The key is then given to the person in charge of team entry before the SCBA team enters a building or structure. The duration of an SCBA’s air supply is based on a number of factors:  The user’s level of exertion.  The user’s physical condition.  The degree to which the user’s breathing is affected by excitement, fear or other emotions.  The degree of training or experience.  The type of apparatus.  The purity of the compressed air (possible presence of carbon dioxide)  Work at pressures above or below normal atmosphere CYLINDER TESTING AND CHARGING Recharging Compressed Air Cylinders In a cascade storage system, several large cylinders are used to bring a small cylinder up to a desired pressure. This is achieved by always using the supply cylinder with the lowest usable pressure first, then the cylinder with the next lowest pressure, etc. A cascade system may be connected to a purification system and air compressor approved for breathable air (CSA Standard Z-180.100). Breathing air cylinders may also be charged directly from an approved breathable air compressor or compressor/storage tank configuration. Recharging Oxygen Cylinders Oxygen cylinders are recharged by transferring oxygen from largecapacity medical-grade oxygen cylinders via high-pressure pump. Hydrostatic testing involves pressurizing a cylinder above its operating pressure to established safety standards to ensure durability of the cylinder over time. The frequency of hydrostatic testing for a compressed cylinder depends on the material and model used. 8-9