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Respiratory Protection [June 2010]

Published: 10th Jun 2010 in OSA Magazine

Relax and take a deep breath

An airborne contaminant is any type of material or gas that does not normally occur in the natural ambient atmosphere. Unlike other types of hazards in the workplace, airborne contaminants are often invisible because of their small size or ubiquitous nature. You may not be able to see, feel or even smell them, however, the lungs are an extremely efficient filter and quickly absorb contaminants from the air we breathe. 

Preventing airborne contaminants from entering the workplace, prohibiting workers from entering such environments and providing adequate ventilation are the first steps that should be taken. Sometimes, however, this is not possible and respiratory protection equipment must be worn.

A critical aspect of the respiratory protection programme is selecting the correct type of respirator for the type of contaminant. Anyone who has ever performed challenging work while wearing a respirator knows that respirators are uncomfortable to wear, cumbersome to use, and interfere with communication. These issues make the selection process important so as to not overly burden workers, but at the same time to provide an acceptable level of protection. It can be generally stated that certain types of respiratory protective equipment are designed to protect you against certain types of some airborne contaminants. Knowing which type of respirator works best in which environment is crucial to the efficient protection of your workforce.

The purpose of this article is to review:

The types of airborne contaminants commonly expected in construction sites, operations, and manufacturing operations

The types of respiratory protective equipment available to protect workers from these hazards

How to correctly fit and use air purifying respirator masks 

How to select the correct type of respirator mask

How to maintain your investment in equipment

Breathing hazards found in the work place

Alveoli are the tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide into and out of the blood takes place. Contaminates in the air we breathe can quickly enter our body via the alveoli or other parts of the respiratory system that lead from the lungs to the nose and mouth. The kinds of hazards which may require the use of respiratory protection include:

Particulate contaminants

Gas contaminants

Oxygen deficiency

The following provides details on these three categories:

Particulate contaminants are solid or liquid particles suspended in the air. These particles can be in many forms such as biological (bacteria, mold, spores, fungi, virus), chemical (consult the MSDS for the compound), dusts, fibres, fumes or mists. The natural filtering mechanisms in the nose and throat usually capture particles in the 5 to 30 micron sizes. Particles 1 to 5 microns in diameter can enter the windpipe and larger branches of the lungs. Particles with diameters less than 1 micron tend to enter the lower lungs and alveolar ducts. Whether these particles damage the body depends on what they are.

Dusts are solid particles which are suspended in the air. Dust is generally created by the cutting, grinding, crushing and handling of solid materials. Silica dust generated by the cutting of bricks and sand blasting is an example of dust that is particularly harmful to the lungs due to its small size and physical structure.

Fumes are solid condensation particles that can range anywhere from 0.1 to 1000 microns. Fumes are commonly found in the air where soldering, welding and brazing work is carried out. Fumes are formed at the tip of the electrode where the electric arc occurs by the evaporation of the metals and fluxes coating the electrode, if used, with the majority of the fumes coming from the electrode wire. These metal vapours are oxidized on contact with air and form small particles composed of a complex mixture of metal oxides. These resulting metal complexes, and thus the respiratory exposure of welders, vary according to the materials and welding processes used.

Mists are tiny liquid droplets given off whenever a liquid is sprayed, mixed or agitated. Spray painting is an example of where mists are formed.

Fibres are solid particles with an aspect ratio of greater than 3:1. Asbestos is a common fibre 

particular contaminant. 

Gas contaminants are toxic gases and vapours which are present as molecules in the air. Their effects vary according to the composition of the gas. Gas contaminants quickly enter the blood system via the alveoli.

Toxicant is any gas that is capable of producing serious injury when entering the body in a sufficient concentration. Examples include hydrogen sulfide, chlorine, ammonia, sulfur dioxide, and hydrogen cyanide. At low concentrations toxicants can be considered to be irritants.

Carcinogens are any air borne compounds of materials that cause cancer. Examples include benzene, formaldehyde and cigarette smoke.

Vapours are formed by the evaporation of liquids. Solvents that are used in spray painting and paint cleaning such as acetone and toluene are contaminants.

Asphyxiants are chemicals that displace oxygen (a simple asphyxiant) or they restrict the body’s uptake of oxygen (a chemical asphyxiant). Nitrogen, hydrogen, helium, methane and halon are simple asphyxiants. Nitrogen is often used in industrial settings to purge other gases that are toxic, corrosive, reactive, or present fire or explosion hazards, making processes safer. Nitrogen is typically used to purge confined spaces that may have toxic contaminants or explosive vapours. A confined space purged with nitrogen is certainly safe from explosion but still presents a deadly hazard to personnel. It’s interesting to note that the normal air we breathe is made up of 79% simple asphyxiant gases. Chemical asphyxiants include carbon monoxide, phosgene and cyanide. 

Oxygen deficiency is a common workplace respiratory hazard. An atmosphere with oxygen content below 19.5% of the atmosphere is harmful to the human body. The lower the percentage is the higher the potential for harm. Oxygen deficiency usually occurs in poorly ventilated areas such 

as confined spaces and typically involves an asphyxiant.

Respiratory Protective Equipment

All industrial countries have regulations addressing respiratory protection requirements. In the US it is addressed by OSHA in 29 CFR 1910.134. The European Union utilises several standards, including: EN149 (disposable filtering face piece respirators), EN 140 (half masks), EN136 (full face masks), EN141 (combination filters), and EN143 (particle filters). Australia and New Zealand use AS/NZS Standard 1715. Canada uses CSA Standard Z94.4-03. These standards provide a solid basis 

for a respiratory protection programme. All of these require employers to select respirators that are appropriate for the chemical state and physical form of the contaminant. Different types of filters, cartridges, and canisters are needed depending on whether dusts, fumes, mists, vapours, or gases are present in your workplace and depending on the kinds and concentrations of the substances present.

The two main categories of respiratory protection are:

Air purifying respirators

Air supplying respirators

A tool used by regulators and suppliers that helps decide which type of RPE to use is the Assigned Protection Factor (APF). The APF of a respirator reflects the level of protection that a properly functioning respirator would be expected to provide to a population 

of properly fitted and trained users. 

For example, most air purifying respirators have an APF ranging from 

10 to 50. An APF of, say 10, is interpreted to mean that a user could expect to inhale no more than one?tenth of the airborne contaminant present. Thus, in the selection of the proper respirator it is critical to know not only the contaminant but the concentration of that contaminant in the ambient air to be breathed, the Permissible Exposure Limit (PEL) and the Short Term Exposure Limit (STEL) for that contaminant. This data should be available on the MSDS or in regulatory information. A credible selection of options can be made using this information.

Air purifying respirators provide protection by purifying the air supplied to the wearer. They work by drawing inhaled air through a filtering medium which reduces the contaminant level in the air before it is inhaled. 

The advantages of air purifying respirators are:

Relatively simple to wear and use

Generally lightweight

Create minimal restriction of movement

The disadvantages of air purifying respirators are: 

They cannot be used in oxygen deficient atmospheres

They do not remove 100% of the contaminant

The filtering medium becomes clogged making it difficult to breathe

Air supplying respirators provide protection by blocking ambient air and supplying stored air or oxygen to the wearer. The air or oxygen is supplied from a different source than the atmosphere the person is working in, such as a compressor, cylinder or air line.

Air supplying respirators are mainly used for: 

Oxygen deficient atmospheres

Highly toxic atmospheres where air purifying cannot filter the contaminant level below the acceptable exposure level

Where full face and body protection is also required

This article only discusses the use of air purifying respirators since they are the most common found in the workplace.

Medical evaluation and fit testing

There are two types of testing required prior to a worker using any RPE device: a medical evaluation to determine whether the individual is physically capable of withstanding the rigours of wearing a respiratory protection device. Once the individual passes this evaluation an HSE specialist or Industrial Hygienist conducts tests to determine whether the device appropriately fits the individual. It is common for people to confuse these two types of tests.

The medical evaluation is a fitness test of the worker. Wearing any type of respirator presents mental and physical challenges to the body. Regardless of the make or quality of the filter the respirator restricts the flow of air into the lungs, restricts movement, impedes normal vision and makes the mind and body work harder in what is already likely to be a stressful environment. Regulations require this type of testing be done by a physician or a licensed health care professional. It is required to be repeated only when the physical condition of the worker changes or the type of mask being worn changes.

The second type of test is a fit test of the equipment to make certain it actually fits the user. Before a worker is allowed to use any respirator he/she must be fit tested with the same make, model, style, and size of respirator that will be used. The fit test can be qualitative or quantitative. In the US an employer is required to conduct fit testing prior to initial use of the respirator, whenever a different respirator face piece (size, style, model or make) is used, and at least annually thereafter. The fit test is much more than a visual check by a co-worker. It must follow detailed protocols provided in the regulations. See Appendix A of 29 CFR 1910.134 for the OSHA fit test protocol.

Disposable respirator masks

Disposable respirator masks are the simplest of all air purifying respirators. They are typically made from a resin coated form-molded filtering material which completely covers the nose and mouth area of the face. The entire mask acts as a filter and traps contaminants as air is breathed in through the material.  Some disposable masks have an exhalation valve. This feature helps to reduce humidity and heat, and reduces resistance when breathing out. Disposable masks work under negative pressure, which means that the air is supplied to the mask when the wearer inhales. Disposable masks are only designed for protection against certain types of particulate materials. The following classification is used by EN149: 2001 to define the classes of disposable respirators:

Class FFP1 protection against non-toxic solid and liquid aerosols in concentrations up to 4 x APF. They have 80% filter efficiency. These masks are for use against mechanically generated particles such as silica and asbestos

Class FFP2 protection against non-toxic and low to average toxicity solid and liquid aerosols (oil mists, for example) 

in concentrations up to 12.5 x APF. 

Masks are used for filtering out mechanically and thermally generated particles such as metal fumes from welding. They filter at least 94% of airborne particles

Class FFP3 protection against non-toxic, low to average toxicity and high toxicity and radioactive solid and liquid aerosols (such as oil mists) in concentrations up to 50 x OEL. Masks remove at least 99.95% of airborne particles

Be certain to read the manufacturer’s data sheet to fully understand the capabilities and limitations of any mask. Also, remember that disposable masks are not effective against asphyxiants, oxygen deficiency, toxic gases or vapours. 

Before donning a disposable respirator mask you should check:

Mask for any physical damage such as holes in the filter material

Edge seal to assure it functions as designed

Straps for adequate tension

Metal nose clip conformance to the shape of the nose

Under the US OSHA regulation an employer is required to select a NIOSH-certified respirator and to assure that the respirator is used in compliance with the conditions of its certification. The US system for classification of disposable filters is as follows:

The following flow chart shows how to choose the most effective type of non-powered, air-purifying, particulate filters and the expected service life using the NIOSH classification standard: 

Notes To Flowchart Regarding Length of Service:

1. The higher the filter efficiency, the lower the filter leakage

2. Limited by considerations of hygiene, damage, and breathing resistance

3. In dirty workplaces (high aerosol concentrations), service time should only be extended beyond eight hours of use (continuous or intermittent) by performing an evaluation in specific workplace settings that demonstrates (a) that extended use will not degrade the filter efficiency below the certified efficiency level, or (b) that 

the total mass loading of the filter is less than 200 mg

4. No specific service time limit when oil aerosols are not present. In the presence of oil aerosols, service time may be extended beyond eight hours of use (continuous or intermittent) by demonstrating (a) that extended use will not degrade the filter efficiency below the certified efficiency level, or (b) that the total mass loading of the filter is less than 200 mg

Disposable mask respirators

General Everyday Fit Requirements

When donning the disposable mask to begin work, make sure that the lower and upper straps are in the correct position and the mask fits tightly against your face. Test the seal around your nose and mouth by covering the filter mask with both hands and sharply inhaling. If there is a proper seal, the respirator mask should collapse back onto your face. If there is not a proper seal you will feel an air stream channeling through the leak. Re-adjust the mask until a proper seal is achieved.

Disposable respirator masks should be replaced as soon as there is any noticeable difficulty in breathing. Large amounts of dust and moisture can quickly clog the filter material. Never attempt to extend the life of a disposable mask by water washing or back-flushing it with air as this will damage the filter material. Once the mask has become clogged it should be immediately disposed of.

To provide adequate protection the mask must be worn at all times while exposed to the contaminant. If you have to remove or adjust the mask, first leave the contaminated atmosphere.

Half-face respirator masks

General Everyday Fit Requirements

Half-face respirator masks are similar to disposable mask respirators but have a more complex design and a higher filtering efficiency. They are made of a rubber or flexible plastic material and are also designed to cover the nose and mouth area. One or two replaceable filter cartridges are screwed into the mask in front of the inhalation valves. The type of cartridge selected will depend on the contaminant and concentration. Half-face respirator masks can be used for protection against particulate contaminants and certain types of gases. The mask is fitted with inhalation and exhalation valves. Half-face respirator masks reduce the level of particulate and gases by passing the contaminated air through an absorbent material contained inside the cartridge. The absorbent can be charcoal or some other special material.

Filter cartridges

The EN141 classification of filter cartridges for the removal of various gases and chemicals utilises lettering and colour code to specify type of component removed, for example:

A - Brown: organic gases and vapors with boiling point > 65°C

AX - Brown: organic gases and vapors with boiling point < 65°C

B - Grey: inorganic gases and fumes (such as hydrogen halogenides, phosgene, hydrogen cyanide, 

hydrogen sulfide)

CO - Black: carbon monoxide

E - Yellow: SO2 and other acid gases (such as  SO2, HCl)

K - Green: ammonia, amines, hydrazine

HgP3 - Red/White: mercury fumes

EN149 also uses a numbering convention to indicate absorption capacity, as follows:

1 - low to medium absorption capacity

2 - medium absorption capacity

3 - high absorption capacity

A gas filter cartridge is designed to be effective in filtering one type or class of gas and as a result may be ineffective in filtering out another type of gas. For this reason it is important to discuss the expected work environmental issues with the supplier. 

Combination particulate and gas filters are also available. These are used where there is a particulate and a gas contaminant in the atmosphere. For example, spray painting generally requires a combination filter because of paint mist and solvent vapours being in the air. Particulate paint mist could rapidly block the gas filter and a particulate filter will not filter out the vapour.

Combination filters can either consist of:

A gas filter with a particulate filter attached to it on the inlet side

A composite filter which provides protection against low concentrations of gas, with a built in particulate filter

Filter cartridges are affected by the concentration of the contaminant, humidity levels and the breathing rate of the wearer. The following checks should be conducted before using a half-face respirator mask:

Face-piece for dirt, cracks or tears

Inhalation valves are clean

Exhalation valves are clean

Filter cartridges are fully screwed into the mask

Head-straps for tears or broken buckles

When fitting the mask make sure that the head straps are in the correct position and the mask fits tightly against your face. Test the seal by covering both filter cartridges with your hands and sharply inhaling. If there is a proper seal the respirator mask should collapse back onto your face. If there is not a proper seal you will feel an air stream channeling through the leak. Re-adjust the mask and check the cartridges are properly screwed in until a proper seal is achieved. Test the seal again by covering the exhalation valves with your hands and gently exhaling. If there is a proper seal there should be a slight pressure build up inside the mask. If there is not a proper seal you will feel an air stream channeling through the leak. Re-adjust the mask until a proper seal is achieved.

Both filter cartridges should be replaced at the same time when:

Breathing becomes difficult

Your nose or throat becomes irritated

You detect any odour or taste

Half-face mask respirators rely on the facial seal to protect you from airborne contaminants. Facial hair such as beards or stubble prevents a proper seal from being maintained. Half-face masks should only be used by a person who is clean shaven. To provide adequate protection the mask must be worn at all times while you are exposed to the contaminant. If you have to remove or adjust the mask, first leave the contaminated atmosphere.

Full-face respirator masks

These masks are also made from a rubber or flexible plastic face-piece but are fitted with a built in clear Perspex lens, so that the entire face can be covered. Full-face respirator masks are fitted with a filter canister which is either connected directly to the face-piece or connected via a flexible tube. Canisters operate in the same way as cartridges but have a much greater filtering efficiency because of their size and the amount of absorbent material they contain. These types of respirator masks are used for protection against highly toxic dusts, gases and vapours, such as hydrogen cyanide gas, where protection is required to prevent contaminants being absorbed into the body through the eyes.

The checking and fitting rules for half-face masks also apply to full-face masks. You must be clean shaven if wearing a full face respirator mask. To provide adequate protection the mask must be worn at all times while you are exposed to the contaminant. If you have to remove or adjust the mask, leave the contaminated atmosphere. With highly toxic gases and dusts even just a few seconds of exposure can result in a fatality.

Care and maintenance of respirators

Employers should provide for the cleaning and disinfecting, storage, inspection, and repair of respirators used by employees. Each respirator user should be provided with a respirator that is clean, sanitary, and in good working order. The manufacturer’s recommendations for care should be followed. Furthermore, the respirators should be cleaned and disinfected at the following intervals:

Respirators issued for the exclusive use of an employee shall be cleaned and disinfected as often as necessary to be maintained in a sanitary condition

Respirators issued to more than one employee should be cleaned and disinfected before being worn by different individuals

Respirators maintained for emergency use should be cleaned and disinfected after each use 

Respirators used in fit testing and training should be cleaned and disinfected after each use

All respirators should be stored to protect them from damage, contamination, dust, sunlight, extreme temperatures, excessive moisture, and damaging chemicals, and they should be packed or stored to prevent deformation of the face piece and exhalation valve.

Summary

Air purifying respirator masks cannot be used as protection in atmospheres that are deficient in oxygen. Make sure that you wear the correct respiratory protective equipment for the type of airborne contaminant that is present. Always check the respirator seal, because without the seal, you are not protected. Wear your respirator at all times where a contaminant is present. Change disposable respirator masks, filter cartridges and canisters as soon as you suspect they are becoming clogged or failing to filter out the contaminant. 

If in any doubt as to what respirator you should be using refer to Material Safety Data Sheets, your Supervisor or Safety Adviser. ?

Author Details:

Michael E Lazarus is a health, safety and environmental advisor living in Cilegon - Banten, one of Indonesia’s youngest provinces located 90km east of Jakarta. Michael is Indonesian. He grew up and spent all his educational time in Malaysia. Mr Lazarus completed his education in Sabah-Malaysia and possesses a Cambridge School Certificate. He has more than 26 years of experience in the Indonesian domestic and Southeast Asia oil and gas industry. Mr Lazarus is enthusiastically involved in fabrication, construction and general services activities. He can be contacted at: mike.e.lazarus@gmail.com

David W Moore is a health, safety and environmental advisor living on Bainbridge Island, Washington, USA. Mr Moore holds a B.S. and an M.Sc. in Chemical Engineering, both from Georgia Tech. He has 38 years of experience in the US domestic and international oil and gas industry. In the past several years Mr Moore has provided significant onsite HSE leadership to the China West to East Pipeline Project (Gansu Province in Western China), the BTC Pipeline Project (Eastern Turkey) and the Tangguh LNG Plant Project (West Papua, Indonesia). Mr Moore is an active member of the American Society of Safety Engineers (ASSE) and can be contacted at: dmoore.che71@gtalumni.org

Published: 10th Jun 2010 in OSA Magazine

Author


David Moore and Michael Lazarus


 

 

Michael E Lazarus is a health, safety and environmental advisor living in Cilegon – Banten, one of Indonesia’s youngest provinces located 90km east of Jakarta. Michael is Indonesian. He grew up and spent all his educational time in Malaysia. Mr Lazarus completed his education in Sabah-Malaysia and possesses a Cambridge School Certificate. He has more than 26 years of experience in the Indonesian domestic and Southeast Asia oil and gas industry. Mr Lazarus is enthusiastically involved in fabrication, construction and general services activities. He can be contacted at: mike.e.lazarus@gmail.com

 

David W Moore is a health, safety and environmental advisor living on Bainbridge Island, Washington, USA. Mr Moore holds a B.S. and an M.Sc. in Chemical Engineering, both from Georgia Tech. He has 38 years of experience in the US domestic and international oil and gas industry. In the past several years Mr Moore has provided significant onsite HSE leadership to the China West to East Pipeline Project (Gansu Province in Western China), the BTC Pipeline Project (Eastern Turkey) and the Tangguh LNG Plant Project (West Papua, Indonesia). Mr Moore is an active member of the American Society of Safety Engineers (ASSE) and can be contacted at: dmoore.che71@gtalumni.org


David Moore and Michael Lazarus

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