Industrial Hygiene and Occupational Health > Chapter - 3 > Personal Protective Equipment > Need of PPE, selection, applicable standard, supply use ,care & maintenance of PPE (Part -2)

Part II of PPE blog-

Sub Topic is Respiratory PPE 

• Classification of Respiratory Hazards 
• Classification of respiratory personal protective devices. 
• Selection of respiratory PPE 
• Instruction and training in the use ,maintenance ,care of self containing breathing apparatus, Training in the use of breathing apparatus (Open circuit and close unit)
• Testing procedures and standards. 

Classification of Respiratory Hazards-

There are three basic classifications of respiratory hazards:

• Oxygen-deficient air
• Particulate contaminants
• Gas and vapor contaminants

1. Oxygen Deficient Air- 

Normal ambient air contains an oxygen concentration of 20.8 percent by volume. When

the oxygen level dips below 19.5 percent, the air is considered oxygen-deficient. Oxygen concentration below 16 percent is considered unsafe for human exposure because of harmful

effects on bodily function, mental processes and co-ordination.

It is important to note that life-supporting oxygen can be further displaced by other gases,

such as carbon dioxide or nitrogen. When this occurs, the result is often an atmosphere that can be dangerous or fatal when inhaled. Oxygen deficiency can also be caused by rust, corrosion, fermentation or other forms of oxidation which consume oxygen. The impact or oxygen deficiency can be gradual or sudden.

Oxygen deficient atmosphere is immediately dangerous to life. The respiratory protective equipment in such conditions should either supply normal air or oxygen to the wear. Self contained or combination breathing apparatus is suitable.

2. Particulate contaminants- 

Particulate contaminants can be classified according to their physical and chemical characteristics and their physiological effect on the body. The particle diameter in microns (1 micron = l/ 25400 inch) is of utmost importance. Particles below 10 microns in diameter have a greater chance to enter the respiratory system and particles below 5 microns in diameter are more apt to reach the deep lung or alveolar spaces.

In the healthy lungs, particles from 5 to 10 microns in diameter are generally removed by the

respiratory system by a constant cleansing action that takes place in the upper respiratory tract.

The various types of airborne particulate contaminants can be classified as follows:

1. Fumes-An aerosol created when solid material is vaporized at high temperatures and then cooled.
2. Dust - An aerosol consisting of mechanically produced solid particles derived from the breaking up of larger particles.
3. Mist- An aerosol formed by liquids, which are atomized and/or condensed.

Types of contaminants can also be classified as under:

1.Toxic particulate contaminants:
These when inhaled may pass from the lungs into the blood stream and are then carried to
the various parts of the body. The effect may be chemical irritation, systemic poisoning or allergic reactions. Common contaminants in this group are antimony, arsenic, cadmium, chromic acid and chromate, lead and manganese.

2. Fibrosis-producing dusts: 
These dusts do not pass into the blood stream but remain in the lungs and may cause pulmonary impairment. The common example under this group are asbestos, coal, iron, bauxite and free silica. 

3.Nuisance Dusts: 
These may dissolve and pass directly into the blood stream or may remain in the lungs
neither producing local nor systemic effects. Examples are saw dust, chalk clay, starch,
cement dust etc.

3. Gaseous Contaminants- 

Gas and Vapour contaminants can be classified according to their chemical characteristics.

In terms of chemical characteristics, gaseous contaminants may be classified as follows:

Inert Gases -These include such true gases as nitrogen, helium, argon, neon, etc. Although they do not metabolize in the body, these gases represent a hazard because they can produce an oxygen deficiency by displacement of air.

Acidic Gases - Often highly toxic (corrosive), acidic gases exist as acids or produce acids by

reaction with water. Sulphur dioxide, hydrogen Sulphide and hydrogen chloride are examples.

Alkaline Gases - These gases exist as alkalis or produce alkalis by reaction with water. Ammonia and phosphine are such examples. 

In terms of chemical characteristics, vaporous contaminants may be classified as follows: 

Organic Compounds - Contaminants in this category can exist as true gases or vapors produced from organic liquids. Gasoline, solvents and paint thinners are examples.

Organo-metallic Compounds - These are generally comprised of metals attached to organic

groups. Tetra-ethyl-lead and organic phosphates are examples. 

Gaseous contaminants can also be classified as:

a) Gaseous Contaminants Immediately Dangerous to life- These contaminants are

gases present in concentrations that would endanger life of a worker breathing them even

for a short period of time. 

b) Gaseous Contaminants not immediately Dangerous to life: These contaminants are gases present in concentration that could be breathed by a worker for a short time without endangering his life but which may cause possible injury after a prolonged single exposure or repeated short exposures.

Classification of Respiratory PPE- 

Classification of Respiratory PPE- Credits- From Book by K.U.Mistry 

Detailing of Classification of Respiratory PPE- 

1) Air Purifying respirators 

2) Air Supplied Devices 

3) Self Contained Breathing Apparatus

1) Air Purifying respirators - 

Air purifying respirators purify the air of gases, Vapour and particulate, but do not supply clean or fresh air. Therefore they must never be used in oxygen deficient atmosphere. Purification of breathing air is done by mechanical filtration, adsorption, chemical reaction or catalysis.

The life of such respirators depends on concentration of the contaminant, scrubbing capacity of the medium (cartridge) and breathing demand of the wearer. The respirator has a face piece and  connected canister (box) or cartridge to purify the air passing through it. 

Main types of air-purifying respirators- 

1. Canister Gas Mask : This consists of a canister, containing appropriate chemical, a full face-piece and body harness to hold the canister. Air is drawn through the canister by the wearer and during its passage through the chemical in the canister the contaminant present in the incoming air is absorbed and reacted with the neutralizer. The canisters are designed for specific gases and it is very important that the appropriate type is used. 

2. Chemical Cartridge Respirator : This consists of a half-mask attached to one or two cartridges. This respirator is a non-emergency gas respirator and it should not be used in an atmosphere deficient in oxygen.

3. Self-rescue type Respirators :

This is designed to provide the greatest possible respiratory protection consistent with the

practicability of carrying the device at all times so that it is always available for use during escape. It consists a filter element, a mouth piece, a nose clip and means of carrying conveniently on the body. The filter elements are similar to chemical cartridge.

4. Mechanical Filter Respirators : These remove particulate matter from the inspired air which passes through a filter. These filters may be of the single use or re-usable type. If these respirators are used in heavy concentrations of particulate matter, the filling will be clogged with dust particles too quickly and they may have to be replaced every now and then,. Micro filters are special filters designed to arrest ultra microscopic size of dust particles and these are used where extremely fine dusts are encountered. Such filters screen out dust, fog, fume, mist, spray, smoke etc. through a filter or pad but they cannot be used against 0 deficiency, gases, solvents and vapors.

5. Combination of Chemical and Mechanical Filter Respirators:

They remove toxic gases and vapors and particulate matter from inspired air. Common example of their use is in spray painting work. They are also known as 'Gas Masks. 

Selection, Instruction and Training in the use of Respirators :

Respiratory protection Programme should include - Policy and administration, identification, measurement, evaluation and control of respiratory hazards. Selection and use of proper respiratory PPE, Training, inspection, maintenance and repair of equipment. Medical surveillance and review of the Programme.

The following factors should be considered for selection of the respirators:

1. Nature of the hazard.

2. Severity of the hazard.

3. Type of contaminant.

4. Concentration of the contaminant.

5. Protection factor which should be > Hazard Ratio = Contaminant concentration / TLV

Assigned protection factors to respirators are as under:

Air purifying respirators - Half mask 10

- Full facepiece 50 

Powered air purifying respirators

- Loose fitting facepiece 25

- Half mask 50

- Full facepiece 1000

Supplied Air respirators (Airline) -

- Continuous flow - Loose fitting facepiece 25 ;-Halfmask50

- Full facepiece 1000

- Pressure demand with full facepiece 1000 SCBA 1000

6. Period for which respiratory protection must be provided.

7. Location of the contaminated areas with respect to a source of respirable air.

8. Expected activity of the wearer, and

9. Operating characteristic and limitations of the available respirator.

Instructions for care should include the following aspects for Air Purifying Respirators :

1. Why and how it is to be used.

2. Protecting the equipment from dust, heat, moisture, extreme cold and damaging chemicals.

Storing in a dry cool place.

3. Checking that it is in good operating condition. Valves should be maintained in efficient working condition.

4. Fitting of respirator on the wearer

5. Proper use and maintenance of the respirator.

6. Cleaning and keeping it in a sealed plastic bag with name tag of the user.

Training for respiratory equipment should include following points :

1. Reasons of need of respiratory protection and limitation or inability of other controls or methods.

2. Identification and understanding of the hazard for which the equipment is to be used and selection procedure;

3. Limitation, capability, function and operation of the respirator.

4. Proper fitting, wearing, adjusting face piece & valves and removing of the respirator.

5. Maintenance and storage procedure.

6. Practice to wear first in a safe atmosphere to become familiar with its characteristics.

7. Practice to wear in a test atmosphere under close supervision of the trainer, and to do similar activities and to detect respirator leakage or malfunction.

8. How to ascertain and handle emergency situation.

9. Statutory provisions regarding use of respirators.

10. When and how to replace filters, cartridges, canisters and cylinders.

11. Instructions for special use if any. The trainer should be qualified safety officer, industrial hygienist, safety professional or manufacturer's representative 

2) Air Supplied PPE Devices- 

1) Airline Respirators- 

Airline respirator consists of a face-piece (half or full mask or a loose fitting helmet or hood) to which air is supplied through a small diameter hose. Airline respirators provide protection so long as the air supply is maintained but the wearer's

travel is restricted by the length of the air supply hose. They are not used in IDLH atmosphere. Air temperature and pressure should be comfortable and the air should be supplied through an air-cleaner. Care should be taken to ensure that the air supply is respirable and is not contaminated and is free from objectionable odors, oil or water mist and rust particles from the supply line.

Types of Airline respirators- 

1) Continuous flow type respirator  

2) Constant demand type respirator. 

2) Suction Hose Mask :

It consists of a full face piece connected to a large diameter flexible hose. The worker draws in air by his own breathing effort, the hose is attached to the wearer's body by a suitable safety harness with safety line and the air inlet end of the hose is provided with a filter to arrest particulate matter. 

3) Pressure Hose Mask (Air supplied hoods): 

This hose mask or hood is similar to suction hose mask except that the air is forced through a large diameter hose by a hand or motor-operated blower or compressor. The blower is to be operated continuously while the mask is in use. 

4) Air-Supplied Suits:

Air line respirators are used where normally nose and face are exposed to hazards and not the other body parts. The air line is connected to the suit 'itself and also to helmet and distributing air evenly throughout on the body, because without such ventilation and cooling effect, it is very difficult and fatiguing to wear such suit for a longer time. 

3) Self Contained Breathing Apparatus- 

They are of two types- 

(1) Self-Contained Compressed Air or Oxygen Breathing Apparatus

(2) Oxygen-Regenerating Recirculating type Self-Contained Breathing Apparatus

(1) Self-Contained Compressed Air or Oxygen Breathing Apparatus- 

This is a device by means of which the wearer obtains respirable air or oxygen from compressed air or oxygen cylinder which is an integral part of the apparatus.

In a demand type Self-Contained breathing apparatus, air or oxygen is admitted to the face piece through a two stage pressure reducing mechanism, only when the wearer inhales and the quantity of air or oxygen admitted is governed by his breathing. The wearer's exhaled breath escapes to the surrounding atmosphere. 

In compressed oxygen cylinder recirculating type breathing apparatus, high pressure oxygen from the cylinder passes through a pressure reducing and regulating valve into a breathing bag. The wearer inhales this oxygen through a one-way breathing valve and his exhaled breath passes into a canister containing chemicals to absorb exhaled carbon dioxide and moisture and then through a cooler into the same breathing bag. Oxygen enters the breathing bag from the supply cylinder only when the volume of gas in the bag has decreased sufficiently to allow the supply valve to open.

From respiratory point of view, self-contained breathing apparatus has no limitation as to the

concentration of the gas or deficiency of oxygen in the surrounding atmosphere but other factors may limit the time that the wearer can remain in a contaminated atmosphere. Many gases are very irritating to the skin and many can be absorbed in dangerous amounts through the unbroken skin.

(2) Oxygen-Regenerating Recirculating type Self-Contained Breathing Apparatus- 

In this type of apparatus moisture content from the wearer's exhaled breath reacts with granular chemical in a canister to liberate oxygen. Also the exhaled carbon-dioxide is absorbed by the chemicals in the canister. The oxygen enters the breathing bag from which the wearer inhales through a corrugated breathing tube connecting the bag to the face-piece. 

Instruction and training in the use ,maintenance ,care of Air Supplied devices and Self Contained Breathing Apparatus - 

Training- 

For proper use of any respiratory protection device, it is essential that the user be properly

instructed in its selection, use and maintenance. Both supervisors and workers must be so instructed by competent persons

Minimum training must include the following:

1. Methods of recognizing respiratory hazards.

2. Instruction in the hazards and an honest appraisal of what could happen if the proper respiratory protection device is not used.

3. Explanation of why more positive control is not immediately feasible. This must include

recognition that every reasonable effort is being made to reduce or eliminate the need for

respiratory protection.

4. A discussion of why various types of respiratory protection devices are suitable for particular

purposes.

5. A discussion of capabilities of the device and limitations.

6. Instruction and training in actual use of respiratory protection equipment and close and

frequent supervision to assure that it continues to be properly used.

7. Classroom and field training to recognize and cope with emergency situations

Precautionary Instructions-  

1. Hazards at workplace must be thoroughly studied, gas, oxygen, contamination, noise etc. should be measured and their level should be minimized by engineering controls first and then only the need of necessary personal protective equipment (PPE) should be ascertained.

2. PPE should be kept ready and in sufficient number. Gloves, shoes, goggles, aprons, earplugs etc. should be given individually and kept clean by the worker in his locker.

3. PPE should be of approved (IS) quality and tested before use. Manufacturer's instructions,

limitations, time limit if any, procedure or method of use, symptoms of malfunctioning, emergency action if it does not work and instructions for maintenance and care should be well

understood before using any PPE.

4. Written instructions should be prepared and displayed or given to the workers for the safe use of the equipment. After medical examination of the worker, need and type of the equipment shall be reconsidered. Change if any, should be incorporated.

5. Laziness in using PPE is not good. A cloth in place of effective respirator is insufficient. Avoiding PPE because the use is for a few seconds or minutes, is unsafe.

6. Loose PPE should be kept away from the moving machine parts.

7. While entering in a tank or working at height, safety belt must be worn, in addition to good sitting and supporting arrangement (safe platform or fencing). Gas and oxygen level should be measured and kept safe as far as possible. PPE shall be selected based on its level.

8. Cotton clothing in hot days, woolen clothing in cold days and tight fitting clothing while working near machinery are 'basic requirement. Synthetic cloths are unsuitable to health. PPE on cotton clothing gives more comfort.

9. A man working on electricity should wear nonconductive helmet. Conductive shoes or clothing are required to discharge static electricity induced in a human body. 

When gas concentration is more than its safe limit or within explosive range (between LEL

and UEL) or oxygen is less than 18% in a tank, (or confined space), it should be ventilated by

air (not by oxygen), the levels should be again measured and when they are safe, permit to

enter should be signed.

10. Air supplying hoods are useful in hot or dusty atmosphere to work for a longer time.

11. Where atmospheric pressure is more than 2 bar, oxygen SBA should not be used because of the possibility of oxygen poisoning. Quick start canister used in closed circuit oxygen self generating (recirculating) SBA, may prove dangerous in atmosphere of gas having less than

315 °C auto ignition temperature. Venting device to release excess oxygen is required in that

case. Used canister should be disposed safely. SBA should be used by a healthy and trained

worker only.

12. In empty air cylinder, oxygen should not be filled. It may cause fire due to contact with oil or grease. 

Maintenance : 

It is a cooperative activity between the employee who takes care of his equipment and the safety professional who teaches him how to use it and provides proper instructions. After inspections, cleaning and necessary repair, personal protective equipment shall be stored to protect against dust, sunlight, heat, extreme cold, excessive moistures or damaging chemicals to retain its original effectiveness. When in doubt about the maintenance of any type of personal protective equipment, it is a good practice to contact the manufacturer. All PPE should be cleaned and examined after each use. Respirators should be cleaned

daily. Face-piece should be washed in warm water with soap or a detergent. Filter and chemical cartridge should be replaced when needed.

Selection of Respiratory PPE- 

Respiratory protective devices vary in design, application and protective capability. Thus,

the user must assess the inhalation hazard and understand the specific use limitations of available equipment to assure proper selection.

The respirators fall under two classifications: air-purifying and air-supplied. 

Air-purifying respirators are used against particulate, gases and vapors. These include negative-pressure respirators that use chemical cartridges and/or filters; gas masks; and positive pressure units such as powered air-purifying respirators (PAPRs), 

Air-supplied devices rely on a primary air source to deliver a steady flow of respirable air to the user's facepiece. These include SCBA and airline devices.

Testing Procedures and Standards- 

Fit Testing

Respirators should fit properly to provide protection. To obtain adequate respiratory protection, there must be a proper match between respirator and wearer. Respirators not properly fitting cause illusion of protection. To accommodate the variability of face size characteristics among individuals, a number of manufacturers offer face pieces in several sizes and models.

Purpose:

The primary purpose of tit testing is to identify the (1) specific make (2) model, style and

size of respirator best suited for each employee.

In addition, fit testing also provides an opportunity to check any problem with respirator

wear, methods of donning and wearing the respirator.

Requirement:

1. Fit testing is required for all negative or positive pressure tight-fitting facepiece respirators.

2. The OSHA respiratory protection standard requires that tit testing be performed before an

employee first starts wearing a respirator in the work environment, whenever a different

respirator facepiece is used, and at least annually thereafter. 

Method:

Prior to the actual fit test, the employee must be shown how to put on a respirator

Position it on the face, set strap tension, and determine an acceptable fit. Next, the

employee must be allowed to choose a respirator from a sufficient number of models and sizes so that the employee can find an acceptable and correctly fitting respirator.

Once an acceptable respirator has been found — which considers the position of the mask

on the face, nose, and cheeks; room for eye protection; and room to talk — a user seal

check must be conducted.

Types of Fit Testing-

• Fit testing may either be qualitative (QLFT) or quantitative (QNFT)
• Prior to the commencement of the fit test, the employee must be given a description of the fit test and a description of the exercises that he or she will be per forming during fit testing.
• The respirator to be tested must be worn for at least five minutes before the start of the fit test.
• The employee must be fit tested with the same make, model, style, and size of respirator that will be used in the workplace. 

Qualitative fit testing (QLFT)-

Qualitative fit testing involves the introduction of a gas, vapor, or aerosol test agent into an

area around the head of the respirator user.

A determination is then made as to whether or not the wearer can detect die presence of the

test agent through means such as odor, taste, or nasal irritation. If the presence of the test agent is detected inside the mask, the respirator fit is considered to be inadequate.

There are four qualitative fit test protocols approved in OSHA's standard -

1. The ISO-amyl acetate (IAA) test determines whether a respirator is protecting a user by

questioning whether the user can smell the distinctive odor of IAA.

2. The. irritant smoke (e.g., stannic chloride) test involves a substance that elicits an

involuntary irritation response in those exposed to it.

3. Before conducting a qualitative test, the worker must undergo a sensitivity test to

determine if he or she can taste, smell or react to the substance.

4. When performing the iso-amyl acetate test, the protocol requires that separate rooms be

used for the odor screening and fit tests, and that the rooms be sufficiently ventilated to

ensure that there is no detectable odor of IAA prior to a test being conducted.

Quantitative fit testing (QNFT)- 

In a quantitative fit test, the adequacy of respirator fit is assessed by numerically

measuring the amount of leakage into the respirator.

This testing can be done by either generating a test aerosol as a test atmosphere, using

ambient aerosol as the test agent, or using controlled negative pressure (CNP) to measure the volumetric leak rate. Appropriate instrumentation is required to quantify respirator fit.

Fit Test Exercises:

The following test exercises must be performed for all fit testing methods:

- Normal breathing in a normal standing position, without talking. Deep breathing in a normal standing position, breathing slowly and deeply, taking precaution not to hyperventilate. 

- Turning the head slowly from side to side, while standing in place, with the employee holding his/her head momentarily at each extreme so that the employee can inhale at each side 

- Moving the head up and down slowly, while standing in place, inhaling in the up position when looking toward the ceiling. 

- Bending at the waist as if to touch toes (jogging .in place can be done when the fit test

enclosure doesn't permit bending at the waist); and normal breathing (as described above).

Retesting:

If the employee finds the fit of the respirator unacceptable, he or she must be given a

reasonable opportunity to select a different respirator and to be retested. In addition, retesting is required whenever an employee reports, or the employer, supervisor, or program administrator observe changes in an employee's physical condition that could affect respirator fit. 

Such conditions include, but are not limited to, facial scarring, dental changes (e.g., wearing new dentures), cosmetic surgery, or an obvious change in body weight.

Facepiece Positive and/or Negative Pressure Checks: 

1. Positive Pressure Check

Close off the exhalation valve and exhale gently into the facepiece. 

The fade fit is considered satisfactory if a slight positive pressure can be built up inside the

facepiece without any evidence of outward leakage of air at the seal.

2. Negative Pressure Check

Close off the inlet opening of the canister or cartridge(s) by covering it with the palm of the

hand(s). Inhale gently so that the facepiece collapses slightly and hold your breath for ten seconds. If the facepiece remains in its slightly collapsed condition and no inward leakage of air is detected, the tightness of the respirator is considered satisfactory. 

Please refer the link of part I of the PPE Blog on Non-Respiratory PPE.

https://niranjanprasad.blogspot.com/2023/07/industrial-hygiene-and-occupational.html 

References: 

• Fundamentals of Industrial Safety and Health- K.U Mistry
• NSO Notes of Industrial Hygiene and Occupational Health 
• Google.com