How to Use Self Contained Breathing Apparatus - SCBA
How to Use Self Contained Breathing Apparatus - SCBA
Introduction
There are many times when hazardous
waste workers will need to use self-contained breathing apparatus (SCBA) to
provide respiratory protection. This chapter provides some general instructions
for the donning and doffing of SCBA, as well as information on emergency
operations. However, every model is a little bit different. Response personnel
must familiarize themselves with the specific units they have available to
them.
Donning SCBA - Coat Method
Self-contained breathing apparatus can be donned like a coat, putting one arm at a time through the shoulder strap loops. The unit should be arranged so that either shoulder strap can be grasped for lifting.
Start by checking the cylinder gauge to make sure that the air cylinder is full. Open the cylinder valve slowly and listen for the audible alarm as the system pressurizes. Then, open the cylinder valve fully. If the audible alarm does not sound, or if it sounds but does not stop, place the unit out of service. Tag it so that no one else attempts to use it.
Have your partner lift the SCBA, bottle
valve down, and hold it behind you at the proper height. Place your arms
through the shoulder straps one at a time. Lean slightly forward to balance the
cylinder on your back. Tighten the shoulder straps by pulling them outward and
downward. Sometimes it will be necessary to lean forward with a quick jumping
motion to properly position the SCBA on the back while tightening the straps.
Continue leaning forward while you fasten the chest buckle if the unit has chest straps. Tighten the shoulder straps future if necessary. Fasten and adjust the waist strap until the unit fits snugly. Finally, recheck all straps to see that they are correctly adjusted.
The SCBA Facepiece
The facepiece for most SCBA are donned
in a similar fashion. However, facepiece from different units often have
different features. Different models may have a different number of straps. The
shape and size of facepiece lenses may differ. And, some units will have the
regulator attached to the facepiece while others may be mounted on the waist
belt. Despite these differences, the uses and donning procedures are
essentially the same. The SCBA facepiece
must be worn properly, for an improper seal may permit inhalation of toxic
gases. The facepiece will not seal against the face properly if its worn
loosely. Long hair, sideburns, or beards can prevent contact between the face
and the facepiece, resulting in a bad seal. Facepiece fit can also be affected
by such things as glasses or missing dentures.
The user should not rely solely on tightening facepiece straps to ensure proper fit. A facepiece tightened too much will be uncomfortable or may cut off circulation to the face. Each person must be fitted with a facepiece that conforms properly with the shape and size of the face. For this reason, many SCBAs are available with different sized facepiece. Nose cups, if used, must also fit properly.
The facepiece for an SCBA with a
harness-mounted regulator will have a low-pressure hose, or breathing tube,
attached to the facepiece with a clamp or threaded coupling nut. The facepiece
may be packed in the case or stored in a separate bag or coat pouch. Wherever
it is stored, the straps should be left fully extended for ease of donning and
to keep the facepiece from being distorted.
Donning the Facepiece
The following procedures apply to a
facepiece with a low-pressure hose. Again, the procedures for most units will
be similar.
Grasp the harness with your thumbs through the straps from the inside and spread the straps. Push the top of the harness up your forehead to remove hair that may be present between your forehead and the sealing surface of the facepiece. Center your chin in the chin cup and position the harness so that it’s centered at the rear of your head.
Tighten the harness straps by pulling them evenly and simultaneously to the rear. Pulling the straps outward, to the sides, may damage them and will prevent proper engagement with the adjusting buckles. Tighten the lower straps first, then the temple straps, and finally the top strap if there is one.
Check the facepiece seal. Exhale deeply,
seal the end of the low-pressure hose with your bare hand, and inhale slowly.
Hold your breath for 10 seconds. This action allows the facepiece to collapse
tightly against your face. If there is evidence of a leak, adjust the facepiece
and test again.
Check to make sure the exhalation valve is functioning properly. Inhale, seal the end of the low-pressure hose with the palm of your hand, and exhale. If your exhaled air escapes at the edges of the facepiece and does not go through the exhalation valve, keep the low-pressure hose sealed, press the facepiece against your face, and exhale to free the valve. Use caution when exhaling against a sealed facepiece in order to prevent discomfort and possible damage to the inner ear from exhaling forcefully. If you cannot get the exhalation valve free, remove the facepiece from service and have it checked.
Connect the low-pressure hose to the
regulator and open the mainline valve. Check for positive pressure. Gently
break the facepiece seal by inserting two fingers under the edge of the
facepiece. You should be able to feel air moving past your fingers. If you
cannot feel air movement, remove the unit and have it checked.
Doffing the SCBA
If is generally recommend that you do not remove SCBA until after you have completed the decon process. If you are wearing a level B suit with the SCBA on the outside, decon personnel will need to support the air bottle for you while they clean between the unit and your suit. However, regardless of which suit you are wearing and whether the SCBA is on the inside or on the outside, you should leave your mask in place until you have gone all the way through decon and have removed any contaminated clothing.
To remove the facepiece, disconnect the low-pressure hose from the regulator, then close the mainline valve. Grasp the facepiece at the chin and pull the facepiece away from your face and over your head. Loosening the straps slightly first may make it easier to remove the facepiece.
Unbuckle the waist and shoulder straps
on the cylinder harness and loosen them enough to make it easier to remove the
unit. Have your partner assist you as you pull your arms through one at a time.
Once you have removed then unit, close the cylinder valve and bleed down the air in the high pressure hose by slowing turning the emergency bypass valve. Leave the valve open until the bell stops ringing, then secure it in the closed position.
Emergency Operation
Hazardous waste site workers must know how to react properly when a problem occurs with the SCBA. There are some fixes you can do inside of a suit when problems are minor in nature. However, these are very limited. If there is a problem with your breathing apparatus you should plan on leaving the contaminated area immediately. If you are working with a single partner, that person should exit with you. No one should be working alone in a potentially hazardous atmosphere. Ensure a malfunctioning SCBA is placed out of service until it can be repaired.
Realize that some of the problems you
may experience will require you to adjust the SCBA in some manner. Fortunately,
most suits will allow you to remove your hand from the outer glove and pull
your arm in through the suit to make any necessary adjustments. You should
practice this so that you do it easily if you need to.
Insufficient Air Supply
The SCBA is equipped with a warning bell that will activate when the unit has approximately five minutes of air remaining. Personnel should never have to leave an Exclusion Zone because this five minute warning bell has gone off. Proper planning includes making sure that personnel have time to exit the Exclusion Zone and complete decon before running out if air. However, should you hear this bell go off, leave the contaminated area immediately, taking your partner with you.
If you out of air before completing
decon, you can remove your mask while still inside the suit to support your
breathing for a limited amount of time. Decon personnel must have a back-up
plan to quickly get you out of the suit and provide fresh air. If you’re
weaning a level B suit with the SCBA on the outside, decon personnel can
provide you with a fresh bottle so that you do not have to remove your mask
until decon is complete.
Problems with the Pressure Demand Valve
If there’s a problem with the pressure demand valve, open the red emergency by-pass valve. Immediately leave the contaminated area, taking your partner with you.
Free Flow of Air Supply
If the unit is free flowing, you will notice air blowing into the facepiece and out of the exhalation valve. Use the cylinder valve to control air flow, turning it off and on as required to provide sufficient air supply. Immediately leave the contaminated area, taking your partner with you.
Damaged Facepiece or Breathing Tube
Immediately leave the contaminated area,
taking your partner with you. Realize that if something has happened to cause
damage to the facepiece or breathing tube, it may have caused damage to your
suit as well. You could be accidentally exposed to a hazardous atmosphere.
Advise the entry Team Leader so that he or she can take any appropriate follow
up actions.
Summary
Hazardous waste site workers may wear
self-contained breathing apparatus because it’s the most reliable and portable
source of fresh air. It’s important that if there is a problem with the SCBA,
the wearer will understand what can malfunction and is trained how to correct
said malfunction. This article provided some general instructions. However,
personnel must familiarize themselves with the specific units that they will be
using.
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