Respiratory Protection Basics

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American Welding SocietySafety and HealthFact Sheet No. 38 September 2013© 2013 American Welding Society

Respiratory Protection Basics for Welding Operations

American Welding Society8669 Doral Blvd.Doral, Florida 33166E-mail: [email protected]://www.aws.org

Fact Sheet No. 38 – 09/13

AWS disclaims liability for any injury to persons or to property, or other damages of any naturewhatsoever, whether special, indirect, consequential or compensatory, directly or indirectlyresulting from the publication, use of, or reliance on this information. AWS also makes noguaranty or warranty as to the accuracy or completeness of any information published herein.

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RESPIRATORY HAZARDS

Welding fume is a complex mixture of verysmall particles of metal oxides and other

compounds that are released during thewelding process. Fume ingredientsdepend on the make-up of the electrode(stick, wire or filler rod), the base metal,surface coatings and contaminants. Thetype of shielding used (flux vs. gas) is alsoimportant. In addition, when electrodecoatings, fluxes, shielding gases andsurface coatings are burned or exposed toarc radiation, they may give off gases thatcould be harmful, such as carbon

monoxide, ozone, nitrogen oxides,gaseous fluoride and phosgene.

What are the Hazards fromOverexposure?

It is claimed that overexposed weldershave a greater chance of developingbronchitis, airway irritation, lung functionchanges, lung infections (pneumonia), andlung cancer when compared to the general

working population. Welding and its alliedprocesses can result in overexposures tosome forms of manganese in fumes fromspecific types of welding consumables.

Some of these have been reported tocause a neurological impairment known asmanganism.

How Can Welders Be Protected fromOverexposure?

Understand Exposures: To protectwelders it is necessary to understandtheir actual exposures. The amount ofwelding fume and other contaminantsgiven off is influenced by manyvariables. For example, the fume givenoff increases as current or electrodefeed rate increases. Also, fumegeneration is typically much higher forflux-shielded processes than for gas-

shielded processes. The amount offume being given off is only one factoraffecting the amount of fume a weldermight inhale. Because so many thingsare involved, it is difficult to estimate theexposure level for welders. Therefore,when adequate ventilation is in doubt,exposure tests should be conducted tomeasure actual representativeexposures during welding operations.Exposure tests typically involve the

collection of air samples by a qualifiedsafety specialist, such as a CertifiedIndustrial Hygienist. Because eachcomponent of welding fume has unique


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effects and exposure limits, theexposure level of each component mustbe measured separately. For example,exposure tests for stainless steelwelders usually focus on chromium andnickel. (More information on weldingfume and exposure assessment is

listed at the end of this document.)

Exposure Limits: Once the exposureis measured and understood, it can becompared to exposure limits set up toprotect workers. Occupational exposurelimits are typically given as a time-weighted average concentration over anormal eight-hour workday (8-hourTWA). In the USA, OSHA's publishedPermissible Exposure Limits (PELs) are

the legally enforceable standard.However, many choose to follow morecurrent advisory standards such asThreshold Limit Values (TLVs®)published by the American Conferenceof Governmental Industrial Hygienists(ACGIH). Each contaminant measuredmust be compared to its exposure limitsto judge if exposure levels pose a riskor not.

Ventilation and EngineeringControls: Normally, ventilation, orexhaust, or both can be used to keepfumes and gases from the breathingzone and general area. When thisdoesn’t work and exposure limits areexceeded, it is necessary to takeadditional steps. These could includethe use of: fume exhaust guns,additional ventilation devices, fans oreven simple adjustments relative to the

natural air flow.

Keep Away from the Plume (fume): One important factor is the position of

the welder's head relative to the risingsmoke/plume and how well theventilation keeps the plume away fromthe welder’s breathing zone andgeneral area. Take care to position thework and/or ventilation device tomaintain protection at all times.

When to Use Respiratory Protection?

Whenever possible, ventilation systems orother controls should be used to removeharmful fumes and gases. However, thesemay not reduce exposure levels enough.Then in this case another option may be touse a respirator. Various respirators existthat offer their own benefits and limitations.

A summary of common welding respirator

categories is shown in Table 2.

How is the Correct Filter Selected?

Particulate (Dust) Filters: Fume can onlybe captured with particulate filters. Table 1lists particle filter classifications defined bythe National Institute for OccupationalSafety and Health (NIOSH). Always lookfor the NIOSH mark and classification codewhen choosing a particulate filter.

Table 1

Efficiency

Resistance to oil mist

N-Series R-Series P-Series

(notresistant)

(mediumresistance)

(highresistance)

95% N95 R95 P95

99% N99 R99 P99

99.97% N100 R100 P100

The first letter refers to the filter’s

resistance to liquid oil mist. The number


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Table 2

Disposable Half

Facepiece

Elastomeric Half

Facepiece

Powered-Air,

Loose-Fitting

Headpiece

Powered-Air,

Helmet (Hard Hat)

Supplied-Air,

(Loose-Fitting or

Helmet)Description

APF 10 10 25 25 / 1000 * 25 or 1000

Benefits No maintenanceLow unit cost

Fits under any welding

helmet

Light weight

More filter optionsMore size options

Moderate unit costLight weight

Reduced stuffinessCooling effect

No breathing resistance No fit testing

Hard hat optionsAccommodates limited

facial hair

Same as Loose-FittingHeadpiece plus:

Hard hat includedHigher protection factor

Better neck protectionAccommodates facial

hair including some beards

Maximum contaminantversatility

Chilled or heated air No breathing resistance

No filters to change No batteries to charge

Limitations Not compatible withfacial hair

For particles only

Increase heat retention

and stuffiness

Fit-test required

Not compatible withfacial hair

May not fit all

welding helmets

Increase heat

retention and

stuffinessFit-test required

Increased weightHigher unit cost

Increased maintenance

Increased user training

Same as Loose-FittingHeadpiece

Attachment to airlineIncreased weight

Higher unit cost

Requires compressor

*APF refers to Assigned Protection Factor which is the minimum anticipated level of protection provided by each type of respirator worn in accordance

with an adequate respiratory protection program. For example, an APF of 10 means that the respirator should reduce the airborne concentration of a

particulate by a factor of 10 (or to 10% of the workplace concentration). August 2006 OSHA amended 29 CFR 1910.134 by adding requirements for

APF’s. For Powered Air Purifying (PAPR) helmets, the manufacturer must have a Workplace Protection Factor(WPF) or Simulated Workplace

Protection Factor (SWPF) study data to substantiate APF of 1000. Refer to OSHA Final Rule:

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=FEDERAL_REGISTER&p_id=18846

that follows refers to the filter’s efficiency inlaboratory tests. N95 class filters arerecommended for most weldingapplications because welding fume isrelatively easy to filter and oil mist isseldom a factor. There is no harm in usinga higher class filter, provided the worker isfit-tested for the device and medicallycleared. When high hazard compounds,such as lead or cadmium are involved,special regulations require the use of P100class filters. Particulate filters must be

replaced when they become soiled,damaged or difficult to breathe through.

Gas and Vapor Cartridges: Gases andvapors cannot be removed by particulate(dust) filters. They must be removed byadsorption in a bed of activated carbon orother media, depending on the gas orvapor species. Certain vapors must bechanged before they can be captured.This is accomplished by treating activatedcarbon with catalysts. Therefore, it isimportant to select a cartridge that isapproved by NIOSH for the vaporspresent. The approved contaminants will


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be listed on each cartridge label. The mostcommon cartridges used in welding areorganic vapor (black label), acid gas (whitelabel) and organic vapor/acid gas (yellowlabel). The service life (how long it lasts) ofgas and vapor cartridges depends on thechemicals removed and their

concentration. Gas and vapor cartridgesdo not clog like particle filters. They simplybecome used up and allow contaminantsto flow through. In some cases, harmfullevels can be exceeded without beingdetected. Therefore, it is critical that aservice life estimate be calculated for eachsituation. Establish a schedule that tellswhen to change filters. Respiratormanufacturers can help with figuring thisschedule.

Powered Air Purifying Respirators(PAPRs): Battery powered respirators usea motor to pull air through filters and/orcartridges to purify the air. The blowersare usually belt-mounted and push filteredair through a headpiece breathing tube.Because the filtered air is under pressure,leakage of contaminants into the helmet isgreatly reduced. This increases the level ofprotection. The movement of air helps

keep the welder cool and comfortable.

Supplied Air Respirators: Some gasesand vapors cannot really be filtered. Inthese cases, a supplied-air respirator maybe needed. Supplied-air respirators requirea compressor, located in a clean area, topump clean air into the respirator. Themain disadvantage of supplied-airrespirators is that the airline makes itdifficult for the wearer to move. Animportant advantage of supplied-air is theability to cool the air. This is a popularfeature in hot welding environments.(Supplied-air must come from a device orsystem that can supply what is known as

“Grade D” breathing air. General shopcompressed air often containscontaminants and should not be used.)

Other Factors

Individual comfort is important. Anuncomfortable respirator will be worn

less consistently. Removal of therespirator, even for short periods oftime, dramatically reduces theprotection.

Welders with facial hair must shave oruse a particular type of powered orsupplied air respirator. Even one-daystubble can cause tight fittingrespirators to leak significantly.

Not all respirators are flame and sparkresistant. Select a respiratorrecommended for welding.

Respirator Program

Before respirators can be used in aworkplace, the employer must have awritten OSHA Respiratory ProtectionProgram in place. Key Elements of theProgram Include:

Training: Training must includeinstruction on respirator use,maintenance, cleaning and storage.Users must be trained prior to use andat least annually thereafter.

Medical Evaluation: Certain lung orheart conditions can make respiratoruse dangerous. Medical clearancemust be obtained before using a

respirator.

Fit Testing: The OSHA standardrequires fit testing for all tight-fitting


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respirator models. Whether you select amaintenance-free or a reusable respirator,the wearer must obtain a satisfactory fit. Fittests must be repeated for each model andwhen any changes occur that could affectthe fit.

Respirator Selection: Describes howa respirator was selected for each task.

Program Evaluation: A process forregularly evaluating the effectiveness ofthe program.

INFORMATION SOURCES

American National Standards Institute(ANSI). Safety in Welding, Cutting, and

Allied Processes, Z49.1, available from American Welding Society, 8669 DoralBlvd., Doral, FL 33166. Phone 800-443-9353; Web site: www.aws.org.

American National Standards Institute(ANSI). Safe Practices For RespiratoryProtection (ANSI Z88.2), available from

ANSI, 11 West 42nd Street, New York, NY10036-8002; telephone: 212-642-4900;web site: www.ansi.org.

Occupational Safety And Health Administration (OSHA). Code Of FederalRegulations, Title 29 Labor, Chapter XVII,Parts 1901,.1 to 1910.1450, Order No.869-019-00111-5, available fromSuperintendent of Documents, U.S.Government Printing Office, Washington,DC 02402.

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