Construction Safety Peer-Reviewed Pneumatic Nail Guns Revisiting Trigger Recommendations By James Albers, Brian Lowe, Hester Lipscomb, Stephen Hudock, John Dement, Bradley Evanoff, Mark Fullen, Matt Gillen, Vicki Kaskutas, James Nolan, Dennis Patterson, James Platner, Lisa Pompeii and Ashley Schoenfisch neumatic framing nail gun use is ubiqui- triggersystemsthatthendefinehowthenailgun tous throughout the modern homebuilding firesinresponsetoatriggerpress: Pindustry.Thistoolhasdramaticallyincreased 1) The sequential actuation trigger (SAT) re- framingproductivitybeyondwhatcouldbeachieved quiresthateachnailcanonlybedischargedwhen with a hand hammer. However, the dramatic in- thesafetytipisfirstdepressedand,whileheldde- creaseinproductivityintroducedanewinjury: pressed,thetriggerissqueezed. You’re using a gun to do something faster, and 2) The contact actuation trigger (CAT) allows fast isn’t safe. It might be making it easier, but theoperatortofirstsqueezethetriggerand,while all around, it’s shooting projectile at a high speed holdingthetriggersqueezed,repeatedlybumpthe to go through hard materials. It’s just dangerous safetytipontheworkpiecetoshootmultiplenails. to work with. (Union carpenter, St. Louis, MO) Ofthesetwotriggermechanisms,theSATpro- Before pneumatic nail guns videsapositivesafetyadvantage(EuropeanCom- were available, nail puncture mittee for Standardization, 2009; Stanley Works, IN BRIEF injuries on a construction site 2002)inthatitpreventstheunintendedfiringof •Use of a pneumatic nail gun with typically occurred when a car- anailthatcanotherwiseoccurwhenthetriggeris a sequential actuation trigger (SAT) penter or other tradesperson depressed and the workpiece contact is bumped significantly diminishes the risk for stepped on a nail protruding (Photo1,p.32). acute traumatic injury compared to use from a piece of lumber. Car- Traumatic injuries can occur when an operator of a nail gun equipped with a contact penters did not accidentally using either type of actuation device intention- actuation trigger (CAT). drivenailsintotheirownbodies allydischargesanailthatsubsequentlypenetrates •A theoretically based increased or that of a coworker with re- throughthewoodormissesitaltogether.However, risk of work-related musculoskeletal peatedstrikesfromahammer. anSAT-equippednailgunismuchlesslikelytobe disorders from use of an SAT nail gun, However,suchinjuriesbecame discharged unintentionally, as the trigger must be relative to CAT, appears unlikely and morecommonwhenpneumat- activated while the safety tip is depressed against remains unproven. icnailgunswereintroducedto theworkpiece(NIOSH/OSHA,2011). •Based on current knowledge, use of drivenailsatahighspeedtogo Unintentional nail discharge using a CAT- CAT nail guns cannot be justified as throughhardmaterials. equippeddevicetypicallyoccursfollowingnailgun a safe alternative to SAT nail guns. Pneumatic nail guns have a recoil (resulting in a double fire—a second, unin- The authors, who are ergonomists and safety device (workpiece con- tendedshot)orwhentheoperatorhashis/herfinger occupational safety researchers, rec- tact,nose,yoke,tip)attheend onthetriggerandthenailgunnoseinadvertently ommend the use of the SAT for all nail ofthegunmuzzlethatmustbe contacts an object (Lipscomb, Dement, Nolan, et gun tasks in the construction industry. depressed before the fastener al., 2003). Although operators are advised to not can be discharged. Generally, hold the trigger in the depressed position when thesedeviceshavetwotypesof notintendingtoshootanail,anailgun’sphysical characteristics,includingweight(8lbto9lb),bal- ance,triggerlocationandhand-gripdesign,make iteasiertoholdthegunwithafullpowergripthat Author Affiliations includestheindexfinger(Photos2and3,p.32-33). •NIOSH:JamesAlbers(retired),BrianLowe,StephenHudockandMattGillen (retired) •DukeUniversity:HesterLipscomb,JohnDementandAshleySchoenfisch Nail Gun Injury Studies •WashingtonUniversity:BradleyEvanoffandVickiKaskutas Portablepneumaticnailgunshavebeenusedto •WestVirginiaUniversity:MarkFullen framenewwoodenstructuressincethemid-1960s •CarpentersDistrictCouncilofGreaterSt.LouisandVicinity:JamesNolanand andgraduallyreplacedtheframinghammerasthe DennisPatterson toolofchoice.Aspneumaticnailgunuseincreased •CenterforConstructionResearchandTraining:JamesPlatner •UniversityofTexasHealthScienceCenter:LisaPompeii inthe1980sand1990s,sodidthenumberofmedi- calcasereportsofpneumaticnailgunfatalitiesand 30 ProfessionalSafety MARCH 2015 www.asse.org traumaticinjuriestothehead,eyes,chest,andthe Lipscomb, et al. (2003), investigated all acute lowerandupperextremities. work-relatedinjuries(n=783)amongaSt.Louis, WashingtonStateDepartmentofLaborandIn- MO,carpenters’unionapprenticecohortworking dustries published the first nail gun injury epide- in the residential building industry (1999-2001). miologyreportin1999(Baggs,Cohen,Kalat,etal., Nearly14%(80)oftheinjuriesinvolvednailgun 1999)andaversionofitwaslaterpublishedinPro- use.Therateforapprenticecarpenterswashigher fessional Safety (Baggs, Cohen, Kalat, et al., 2001). (3.7/100FTEs)thanthatofjourney-statuscarpen- Thestudyreportedananalysisofworkers’compen- ters(1.2/100FTEs).Amajorityofinjuriesoccurred sationclaimsfornailguninjuriesthatoccurredfrom whentheCATmechanismwasusedandtheau- 1990to1998inWashingtonState.Theinjuryinci- thorsconcludedthat65%oftheinjuriescouldhave dentrateforbuildingconstructionworkers(SIC15, beenpreventedhadthenailgunsbeenequipped BuildingConstruction)was78incidentsper10,000 withanSATmechanism. full-time equivalent (FTE) workers/year, while the LipscombandJackson(2007)analyzedreportsof incident rate for wood framing tasks was 206 per nailguninjuriestreatedinU.S.hospitalemergency 10,000FTE. departmentsfrom2001to2005.Therangeinannual Dement, Lipscomb, Li, et al. (2003), analyzed occupationalrelatedinjurieswas19,300to28,600, Ohio Bureau of Workers’ Compensation claims with an annual average of 22,200. Most injuries (1994-97) for all Ohio carpenters and residential weretotheupperextremities(66%)andlowerex- constructionworkersemployed(1996-99)byNorth tremities(24%);bonefractureswereinvolvedin4% CarolinaHomeBuildersAssociationmembers.Nail oftheinjuries.Thedatadidnotincludeinformation gun injury rates for the North Carolina and Ohio describing nail gun actuation systems being used cohorts were 91 cases/10,000 FTE and 132/10,000 whenthetraumaticinjuriesoccurred. FTE,respectively.Asubsetofclaimswasanalyzed Clearly,usingpneumaticnailgunspresentsthe (n=185)thatincludedwrittennarrativedescriptions potential for serious injury or death. An unpub- oftheinjuryincidentandtheauthorsconcludedthat lishedreviewofninenail-gun-relatedfatalityin- atleast69%oftheincidentsmayhavebeenthere- vestigationsintheOSHAIntegratedManagement sultofanunintentionalnailgundischargeormisfire. InformationSystemrevealedthreecasesthatwere www.asse.org MARCH 2015 ProfessionalSafety 31 Photo 1: The full SAT nail gun is safer because it requires that the two con- trols be actuated in a specific sequence. First, the safety tip is pressed against the lumber (left panel), then the trig- ger is depressed to fire the nail (middle panel). When the nail gun fires, recoil of the tool away clearlyattributabletotheCATtrigger(thatis,pre- SATsystems.Forexample,in2001,theNewZea- from the workpiece ventablewithSAT)andfivecasesthatlackedad- landDepartmentofLaborpublished“Guidelines (right panel) can equateinformationtoclearlydeterminetheroleof fortheSafeUseofPortableMechanicallyPowered result in a second, triggertypeincausation.Onlyonefatalitycasewas NailersandStaplers.”Theseguidelinesacknowl- unintended, contact deemed to have been clearly unpreventable with edgeriskofoverusesyndromewithSAT,butonly of the safety tip. SAT.ItisalsoknownthattheSATsystemprovides in high-volume production when “thousands of With the SAT, a apositivesafetyadvantageovertheCATsystem. trigger pulls every day” are required. The New nail will not fire Despitethis,theCATsystemismorelikelytobe ZealandguidelinesonlyallowforCATuseunder on the second usedthantheSATsystem. safelymanagedhigh-volumepalletandwoodcrate contact because OneanecdotalargumentagainstusingtheSAT assemblyoperations(notconstructionwork)when the trigger must systemisthepotentialfordevelopingtriggerfinger anumberofnailgunmanagement,operatortrain- first be released (stenosingtenosynovitis)asaresultoftheneedto ingandworkstationdesignrequirementsaremet. and then actu- squeezethetriggerforeachnaildischarged.Baggs, The authors suggest that theoretical concerns ated after the safety etal.(2001,p.37),provideanopinionthatnailgun aboutthedevelopmentofspecificstenosingteno- tip. Conversely, a operatorsusetheSATsystem.However,theear- synovitissymptomsfromuseofSAT-equippedde- CAT-equipped nail lierSHARPreport(Baggs,etal.,1999)includedthe viceshavenotbeenconfirmedbyeithersurveillance gun fires with the following: orbiomechanicalevidence.ArecentNIOSHstudy controls actuated As employees gain experience with the tool, the conducted to assess finger displacement and pre- in either sequence “bump” (CAT) trigger system can be implement- dictedfingertendontraveldidnotresultincumula- and the trigger need ed to reduce the potential risk of musculoskel- tivetendontravelatthelevelspreviouslyassociated not be released etal disorders (e.g., trigger finger). Manufacturers with hand/wrist musculoskeletal disorders (Lowe, between successive should work with users and safety profession- Albers,Hudock,etal.,2013). nails fired. als to better balance speed and productivity of AsecondNIOSHstudy(Albers,Hudock&Lowe, using the