HƯỚNG DẪN SỬ DỤNG THIẾT BỊ SCBA (SELF CONTAIN BREATHING APPARATUS)

HƯỚNG DẪN SỬ DỤNG SCBA (BÌNH DƯỠNG KHÍ) Thiết bị thở độc lập (Self Contained Breathing Apparatus - SCBA) dụng cụ bảo hộ cần thiết sử dụng lực lượng cứu hộ, lính chữa cháy, người làm việc bên không gian hạn chế hay môi trường thiếu dưỡng khí hoăc tiếp xúc với khí độc Thiết bị thở giúp cho việc hô hấp người sử dụng không bị gián đoạn an toàn tối đa Ngày có hai loại SCBA sử dụng, SCBA tuần hoàn mở SCBA tuần hoàn đóng Điểm khác biệt SCBA tuần hoàn đóng so với SCBA tuần hoàn mở sử dụng hoạt động cấp cứu khoảng thời gian lâu Trong loại này, không khí liên tục tái xử lí để người mặc có không khí sử dụng liên tục Đối với loại SCBA tuần hoàn mở, không khí nén bình chứa áp suất cao sử dụng hoạt động cấp cứu thời gian ngắn Cấu tạo SCBA gồm: - Bình chứa không khí: Trong loại SCBA tuần hoàn mở bình chứa nạp không khí nén (thông thường không khí nén áp suất từ 250 – 300 bar) để người dùng vào khu vực có khói, lửa cứu nạn nhân bị mắc kẹt Bình chứa làm thép composite với dung tích thông thường lít 6,9 lít tùy theo nhà sản xuất - Mặt nạ thở: Mặt nạ thở thiết kế để bao phủ tất phận khuôn mặt, phận bảo vệ mắt suốt để người dùng thấy đường Ngoài có ống nối để chuyển không khí từ bình chứa vào mặt nạ thở - Đai mang vác: Đai mang vác dùng để vác bình không khí sau lưng giúp giữ tất phận SCBA lại với Trên đai có khóa trước bụng dây rút vai, người sử dụng cần điều chỉnh chúng phù hợp với thể để mang bình thoải mái - Đường ống dẫn khí, đồng hồ áp suất, còi báo động van giảm áp Các bước để sử dụng SCBA Kiểm tra phụ kiện Bộ SCBA; Đeo bình chứa khí nén hình minh họa Siết chặt dây đai Bộ SCBA cho phù hợp, thoải mái Kiểm tra mặt nạ để đảm bảo không hư hỏng, Gắn van điều áp vào mặt nạ Kiểm tra áp suất thực Bình khí nén, kiểm tra còi an toàn Đeo siết mặt nạ đảm bảo kín & thoải mái Xả áp từ Bình khí nén & theo dõi đồng áp suất để đảm bảo không tụt áp Điều chỉnh, siết lại mặt nạ để tránh rỏ rỉ Tháo SCBA sau sử dụng Types of Respirators Self-Contained Breathing Apparatus (SCBA) A self-contained breathing apparatus is used when extremely toxic chemicals are present, in an oxygen-deficient atmosphere, or when the contaminant or concentration is not known SCBA's are also typically used in emergency situations SCBA's consist of a bottle (tank or cylinder), carrying assembly, gauge, safety valve, and a full facepiece The bottle is equipped with an alarm to warn the wearer when air in the tank is getting low (about 25% of the tank air remains) Some SCBA's operate in an open-circuit mode; that is, the exhaled air is vented to the atmosphere and not rebreathed Other SCBA's operate in a closed-circuit mode where exhaled air is filtered before it is rebreathed SCBA's differ by manufacturer and type You must be trained in the manufacturer's instructions and inspection procedures before using any SCBA Also, only a certified person may conduct technical repair operations on the unit The key parts of an SCBA other than the air tank, facepiece, and hose include:  The demand regulator, which reduces tank pressure to provide air when the wearer inhales  The main valve (yellow), which controls flow to the regulator This valve should be left open except when the by-pass valve is in use  The by-pass valve (red), which bypasses the regulator in cases of malfunction of the regulator or the main-line valve This bypass should be open only when needed The regulator should not be bled with this valve A positive-pressure SCBA or positive-pressure air-line respirator equipped with an escape air supply must be used when chemical exposure levels arc likely to present an IDLH situation or impair the ability to escape Types of Respirators Donning SCBA's To put on an SCBA, you must follow a number of steps A basic example is given below (Check the instructions provided by the manufacturer for specific procedures.)  Check gauges and valves  Turn on cylinder valve and listen for low-pressure alarm  Put on the tank and harness and adjust straps  Don the facepiece and check the facepiece seal (Fit- testing will be reviewed in the next section.)  Check the main-line and the by-pass valves The equipment should be donned according to the manufacturer's recommended procedures Workers must be trained for each type of SCBA which will be used Routine training and practice is especially important for workers who may use this equipment infrequently When the contaminant is unknown, wear an SAR with egress unit or SCBA Respirator Fit A respirator will only be effective if there is a good seal between the facepiece and the wearer's face Therefore, all persons wearing respirators must first be fit-tested Fit-testing includes qualitative or quantitative testing as well as routine positive- and negative-pressure tests Since many different face shapes exist, SCBA manufacturers offer a number of sizes The purpose of fit testing is to find the manufacturer/size combination which offers the best protection Factors such as beards, weight loss or gain, dentures, dental work, or facial injury can change the shape of the face, thus potentially change the fit and efficiency of the respirator If for any reason any of these factors exist, testing is required A protection factor has been determined in the laboratory for each type respirator (APR, PAPR, SCBA, etc.) and type of mask (half or fullface) Never assume you will get this much protection That is why fitting is required Respirator Fit Periodic Fit-Tests Qualitative or quantitative fit-testing may be used to determine the size and model of the required respirator This will also help determine how well the facepiece fits the face These tests should be repeated periodically to document the respirator's effectiveness Qualitative Testing Qualitative Testing with irritant or smelly substances: PURPOSE: Checks effectiveness of respirator in preventing substances from entering the facepiece METHOD: An individual, while wearing a respirator, enters a chamber or an atmosphere where a test substance has been released The test substance could be smelly (banana oil) or an irritant (special smoke tube) The wearer should not be able to detect the substance REQUIREMENTS: This test or a similar test is required by OSHA 1910.134 (e) (5) and should be done at least once a year There are several important factors regarding qualitative fit-testing  Some of the test substances may irritate the eyes or cause coughing  A poor sense of smell or taste may result in an inaccurate test Fit-testing is often done in "ideal" environments  The fit may change after wearing the respirator several hours or during strenuous activity Quantitative (Numerical) Testing PURPOSE: Measures effectiveness of respirator in preventing substance from entering the facepiece METHODS: An individual, while wearing a respirator modified with a probe, enters a chamber A test substance is released, and the concentrations in the air inside and outside of the respirator are measured (Another version of this method is available which does not require a chamber of a test substance The dust which naturally occurs in the air is measured both inside and outside the respirator.) REQUIREMENTS: This test is not required by OSHA, but it should be done at least annually if the service is available This test provides an objective assessment of the effectiveness of the respirator for the person who will wear the respirator This test measures the fit factor (FF), which is a comparison of the concentration of the substance outside of the mask to the concentration of the substance inside of the mask This FF is useful in determining if the respirator will effectively protect the wearer from specific chemicals A disadvantage to the test is that special equipment and trained personnel are needed to administer it, although a microcomputer and software accessories can perform the calculations required Respirator Fit Routine Fit-Test Two types of testing, positive and negative-pressure test, should be done each time a respirator is donned and before each use of a respirator in the field to check the seal of the respirator They not replace yearly fitting but provide a routine assessment as to whether or not the fit is still adequate Positive-Pressure Test PURPOSE: Checks the apparatus for leaks at valves or other points METHOD: Wearer covers the exhalation valve with hand and blows out Air should escape only from around the facepiece REQUIREMENTS: Should be done before each use Negative-Pressure Test PURPOSE: Checks the facepiece-to-face seal METHOD: SCBA wearer disconnects the hose mask and places hands over the intake valve and inhales APR wearer places hands over cartridges and inhales No outside air should be felt leaking into the facepiece REQUIREMENTS: Should be done before each use Positive and negative-pressure tests can be done quickly and easily in the field They do, however, have the disadvantage of relying on the wearer's ability to detect the leaks Minimum Requirements For A Respirator Program OSHA requires that employers who make respirators available to their employees must have a written respirator program The program should be evaluated at least annually or as requirements change, and modified to reflect changes in the workplace A respirator program must include the following points  Written standard operating procedures for selection and use  Selection criteria based on hazards  Instruction and training for wearer in use and limitations  Regular cleaning and disinfecting  Clean, convenient, sanitary storage  Respirators that are used routinely should be inspected during cleaning and worn parts should be replaced Emergency-use respirators need to be inspected monthly and after each use  Maintain appropriate surveillance of work area conditions, employee exposure, and employee stress  The program should be reevaluated on a regular  Medical evaluation for those who use respirators  Use only approved or accepted respirators The respirator program may also include:  Need for corrective lenses in full-facepiece respirators  Restriction on use of contact lenses  Communication needs  Guidelines for use in dangerous atmospheres, including permit spaces  Guidelines for use in extreme temperatures The respirator program will include a description of who is responsible for the various aspects of the program including selection, periodic and routine fit-testing, inspection, cleaning, repair, and maintenance Persons using respirators under unusual conditions (e.g., high concentration of add vapors) should review special requirements with supervisors or the employee safety and health representatives Protective Clothing Personal Protective Equipment (PPE) provides protection against hazardous substances PPE includes respirators, chemical-protective clothing (CPC) hard hats, boots, safety goggles, and face shields PPE provides an important barrier between chemicals or other hazards in the environment and your body Although PPE cannot provide protection from all exposure, when properly selected and worn, it can prevent unnecessary, harmful exposures This section will describe several combinations of PPE used when entering permit spaces