IRII 93831 REPORT OF INVESTIGATIONS/ I 99 1 

Self-Contained Self-Rescuer Donning 

Proficiency at Eight Eastern 

Underground Coal Mines 

By Charles Vaught, William J. Wiehagen, 

and Michael J. Brnich, Jr. 

UNITED STATES DEPARTMENT OF THE INTERIOR 


BUREAU OF MINES 

Mission: As the Nation's principal conservation 

agency, the Departmentof thalnterior has responsibility for most of our nationally-owned public 

lands and natural and cultural resources. This 

includes fostering w ise use of our land and water 

resources, protecting our fish and w ildlife, preserving the environmental and cultural values of 

our national parks and historical places. and providing for the enjoyment of life through outdoor 

recreation. The Department assesses our energy 

and mineral resources and works to assure that 

their development is in the best interests of aI/ 

our people. The Department also promotes the 

goals of the Take Pride in America campaign by 

encouraging stewardship and ci tizen respons ibility for the publ ic lands and promoting citizen participation in their care. The Department also has 

a major responsibility for American Indian reservation communities and for people who live in 

Island Territories under U.S. Administration. 
Report 01 Investigations 9383 

Self·Contained Self·Rescuer Donning 

Proficiency at Eight Eastern 

Underground Coal Mines 

By Charles Vaught, William J. Wiehagen, 

and Michael J. Brnlch, Jr. 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Manuel Lujan, Jr., Secretary 

BUREAU OF MINES 

T S Ary, Director 
Ubrary of Congress Cataloging in Publication Data: 

Vaught, C. 

Self-contained Klf-lUCIIer donning proficiency at eight eastern unde1J.tOund coal 

mines / by Charles Vaught, William J. Wieha~n, and Michael J. Bmith, Jr. 

p. em. - (Report of invutiptiOl\l; 93&3) 


Includes bibliognphical references (p. 11). 


1. Self-contained 1iC1(-res<:uer (Mine rucue equipment). 2. Coal minen-East 

(U.5.rRaling of. 1 Motor abilit)'-Tcsting. I. eh ~n, William J. U. Bm)ch, 

M. J. IIJ. Title. tv. Series: Report of invuliptKm1 (United Stales. Bureau of 

Mines); 9383. 

TN23.U43 (TN297] 622 ,--<leW (622'.891 91·10025 C1P 
CONTENTS 


Abstrad. . . . . . . . . . . . • • • . • • • . • . . . . . . . . . . . . . . . . . . . . . . . . . • . . . • . • • . . . • • • • • . . . . . • . •• • • . . . 

P.". 

1 


Introduction .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • • . . 2 


Procedure ...... . ... ....... ... .. • • • • • .•........ . .•...... . .... ...... . . •••• . •••••• ••. 2 


Sampling mines and miners . . . . .. ...... ........... .............. .. .... ......••• ••••.. 2 


EvalualiDg doDDiDg performance . . . • . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . • . . . . . • . • • • • • • • . . 2 


A.s.cessjng proficiency levels . . . . . • • • • • • • . . . . . . . . • • . • . . . • . . • . • • • • • • • • . • . . . . • • • • • • • • . • • • . 3 


Proficiency levels at eight mines . ...... • ••• •••••• . • ... •••••••••••• . ••••• • • • • • • •• •• •••. .. . 5 


Error profile of sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • . • . . . . . 13 


Sampling aud quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . • • • • • • . • . . • . . 14 


Discussion . . . ... ........ . . . ... .. . ... ......... . ...................... ••.• • •• • • • . . ... 16 


References ... . . . . . . . . . . . . . . . • . • • • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . • • . . • • • • . • • • . • • . 17 


ILLUSTRATIONS 

1. Evaluation form. for use in teaching and assessing 3 +3 donning method . . . . . . • • • • • • • • . . . . . . . . . . . 4 


2. Evaluation form. for failing performance .. . . . . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • . • . . . . . . . . . . . 6 


3. Evaluation form for poor performance ... . . . . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • . . . . . . . . . . . . . 7 


4. Evaluation form. for marginal performance . . . . . . . . . . . . . . . . . . . . . . . • • . • . • • • • • • • • . . . . . . • . . . 8 


5. Evaluation form for adequate performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . 9 


6. Evaluation form for perfect performance ................................ . .......... .. .. 10 


7. Donning proficiency profLies for samples at eight mines ........ . .......... .. ............... 11 


8. 	 Comparison of donning proficiency 1 week after training at mine A with proficiency at western mine 


1 week after training ...................... . ....... .... .... . . . . . . . . . . . . . . . . . . . . . . . 12 


9. Confidence intervals ............................. ...... ........................... 15 


10. Percentage of miners failing to isolate their lungs ........ . . . ••••••••• ..................... 16 


TABLES 

1. Donning errors by mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 


2. Percentage of miners who put nosedips on before mouthpiece ....................... ....... . 13 


3. Percentage of miners who put nosedips on before mouthpiece and subsequent1y failed . . . .......... 14 


4. Failures due to mouthpiece errors ................... .. .......... . . . ......... . ........ 14 

UNIT OF MEASURE ABBREVIATION USED IN THIS REPORT 

JK1 percent 
SELF·CONTAINED SELF·RESCUER DONNING PROFICIENCY 


AT EIGHT EASTERN UNDERGROUND COAL MINES 


1 By Charles vaught,

l Research socioiogisi. 

W 2 illiam J . Wiehagen.

lsupcNisory industrial engineer. 

and Michael J. Bmlch, Jr.3 

lMining engineer. 

Pittsburgh Research Center, U.S. Bureau of Mines, Pinsbur&:h. PA. 

ABSTRACT 

The U .S. Bureau of Mines evaluated the se lf-co ntained self-rescuer (SCSR) donning profi ciency of 

243 miners. These workers were from eight underground coal mines in the eastern U nited States. The 

objectives of the study were (1) to gather information on sk ill levels, since all miners in the study bad 

prior instruction and opportunity to practice donning the apparatus, and (2) to summarize a quality 

control procedure useful in conducting periodic evaluations of donning proficiency. The sampling 

procedure used proved to be both reasonable and efficie nt in gathering information on training 

effectiveness. It also provided a good statistical base for making inrormed site-specific decisions 

rcgarding SCSR training needs. Results (rom the observed samples at each of tbe eight mines indicate 

a wide variability across sites. The rate at which miners railed to isolate their lungs varied (rom 3.3 to 

40.0 pet. Concomitantly, profi ciency rates (miners either performing adequ ately or demonstrating a 

perfect 3+3 sequence) ranged from 13.3 to 63.3 pet. 
2 

INTRODUCTION 


SCSR training dates 10 mandatory deployment (I).

"Italic nl.LmDe" in parenthescs refer to items in the list of references 

at the end of this repon. 

of 

the apparatus in underground coal mines in J981. Queslions about the n3ture and quality of this training, and 

ahout the ability of workers to usc the device, were transialed into specifi c regulatory action in 1987 and 1988 (2-3). 

The resulting regulation required mine operators to include a hands-on component in their SCSR training. Information on miners' donning skills is not typically 

gathered, however. Additionally, miners are not usually 

refreshed or evaluated between training cycles. Hence, the 

con tent of annual SCSR instruction is fairly static, with 

federa l and Slate requirements providing the impetus for 

most retraining. 

O ne shou ld not assume that once-a-year practice in a 

classroom leads to SCSR donning proficiency. Such an 

assumption relegates the training to simple compliance 

with regulations, and does nOI necessarily resu h in 

adequate donning skills. Be tter ties between training and 

performance, however. arc only possible through the collection of proficiency data. In short, attempts to improve 

the training process are likely to be ineffective unless they 

arc linked to an empirical base. 

This study was designed as an empirical assessment of 

SCSR donning profici ency and for providing a set of sampling guidelines useful in determining, at the mine-wide 

level, the s kills of underground workers. From January 

through March 1989, the U.S. Bureau of Mines participated in an evaluation of SCSR donning at eight sites in 

the easte rn United States. The evaluation was with a 

canvass being conducted by the Mine Safety and Health 

Administration (MSHA), although the Bureau's activity 

was considered to be an independent research project. A 

brief report of the procedures used and a discussion of the 

findings follows. 

PROCEDURE 


This section details the procedu re used to select the 

mines and miners comprising the study sample. It also 

discusses the methods used to collect performance data 

and to differentiate donning proficiencies. 

SAMPLING MINES AND MINERS 

Researchers obtained a listing of candidate mines in 

a limited geographic area. They next determined the type 

of SCSR in use at each of these operations. The mines 

were then grouped by apparatus (MSA, CSE, Ocenco, and 

Draeger),'

'Reference to specific prodl.Lcts docs not imply endof$emen! by the 

U.S. Bureal.! of Mines. 

and two mines were randomly se lected from 

each category. The MSHA education and training specialist responsible for evaluating each particu lar mine was 

then contacted, and a rrangements were made for a mutually convenient time to conduct the on-site assessment. 

At the mine, an underground section was selected 

randomly for evaluation. If the mine produced on more 

than one shift, the researchers stayed on that section and 

evaluated all workers (until a total of at least 30 had been 

obtained). If the mine prod uced o nly on one shift, or if 

there was no possibility of sampli ng 30 workers on the 

initial section selected, a second section was drawn randomly for inclusion in the sample. 

The data collection protocol required two researchers 

to evalu ate each donning trial. Once the evaluation team 

arrived on an underground section, miners were brought 

back from the face one at a time. One of the Bureau 

investigators explained that this study was concerned with 

how well miners could put on the SCSR in the event of an 

emergency. The subjects were informed that their coope ration in the study was strictly voluntary. After receiving the worker's consent to participate, (nobody refused). a short interview was conducted to obtain basic 

demographic data such as age, expe rience, and job tit le. 

It was explained to the individuals that they should don the 

SCSR just as they would if it were necessary to escape the 

mine, and to do the entire procedure.

6 

611le miner ...-as told that a cleaned and disinfected mOl.Lthpic« 

assembly had jllSt b<:en installed on the train;n, model and ...-as shown 

the n:maining sl.Lpply of disinfccted mouthpiece aslCmblics, each 

packaged in iu own clcar plastic bag. 

One of the evaluators next requested the miner's pe rmil>:>ion to videotape 

the donning trial, explaining that the videotape would be 

used to verify the donning evaluations. Finally, the 

worke rs were asked to place themselves behind an SCSR 

training simulator, which was resting on the mine noor and 

to prepare to don t he device. 

EVALUATING DONNING PERFORMANCE 

At a signal from the evaluator operating the video camera, the mine rs donned the SCSR (without prompting) and 

signaled that they had finished by raising their hand. 

While one researcher videotaped the entire procedure, the 
3 

other evaluated and timed the trial. If an individual decUned to be videotaped, both evaluators noted and timed 

tbe performance so that results could be cross-checked 

A total of 243 miners were evaJuated. One mine, mine 

G, refused to allow videotaping. In addition, 27 individuals 

at other operations declined to be videotaped. In all, 

however, researchers were able to collect 185 videotaped 

performances to compare with initial evaluations. In some 

cases (less than 10 pct), an analysis of the videotapes led 

to alterations of the original assessment. In the case of 

those for whom there were no videotapes, the two evaluators looked over their forms and, where there were discrepancies, reached an agreement on the resolution. The 

only other potential problem in finalizing the data 

occurred with those miners who refused to insert the 

mouthpiece. As it turned out, there were only four miners 

in this category. The data from their trials was treated as 

missing information. In summary, the preliminary analysis 

that follows is based on data that have been closely 

scrutinized, and is an accurate representation of the 

proficiency levels found in the sample at the eight mines. 

ASSESSING PROFICIENCY LEVELS 

Donning performance and profi ciency were assessed 

using the evaluation form (fig. 1) distributed by the 

National Mine Health'and Safety Academy as part of the 

3 +- 3 SCSR instructional package (4). Use of this form has 

two primary functions: (1) as an instrument to measure 

an individual's donning performance, and (2) as a feedback 

device to the individual performing the task. Accurate 

knowledge of results is neccssary on both an individual and 

group level. Without feedback to the trainee, there is not 

likely to be any skill improvement. For those who allocate 

training resources, detailed information about patterns of 

group actions offers a valuable baseline of performance to 

target for improvement. 

The 3 +- 3 evaluation system allows researchers to make 

reasonably fine distinctions among donning proficiency 

levels. To assist in examination of the performance data, 

a five-fold typificatioo was used, dependent upon the 

degree of proficiency demonstrated. In the final analysis, 

whether one passes or fails in the real world would be 

determined by the ability to use one's SCSR well enough 

to survive an attempt to evacuate through an unbreathable 

atmosphere. There is little doubt, however, that someone 

who can put on and use the apparatus with some degree 

of competence will have a better chance than someone 

who cannot. 

Descriptive comments taken from actual evaluation 

forms are profiled below: 

FQiling: FQiluTt (0 iJolQ(t lungs 

• The mouthpiece flange was outside the miner's ups 

and miner did not adjust straps. 

• The miner put the SCSR on backwards. The mouthpiece and noseclips pulled out· miner put the mouthpiece 

back in, but forgot the noStcups. The miner did not adjust 

the waist or neck straps. 

• The miner failed to activate the oxygen and forgot 

to put 00 the noseclips. 

P()()I': LungJ jJolattd but not tJCQPt /'tQdy 

• The miner stood up to put the SCSR 00. The 

mouthpiece and noseclips pulled out because the trainee 

fail ed to adjust the neckstrap. The miner appeared to be 

very confused during the entire donning sequence. 

• The miner did not loop the neckstrap. Instead, miner put the waist strap around the neck. The miner also 

put the goggles on over the glasses and forgot to put the 

hardhat back on. 

• The miner failed to adjust the neckstrap; as a result, 

there was noticeable tension on the breathing hose. 

MQrgina/: ConfwionJ that could CQUJt tJCQpe problttTU 

• The miner twisled the neckstrap around the breath· 

ing hose. 

• The miner did not put on the goggles and failed to 

fasten the waist strap. The nosec1ips slipped off, but the 

miner put them back on. 

• The miner adjusted the neckstrap after looping. but 

never secured the waist strap. The miner took the mouthpiece out to look for noseclips, and put it back in once 

they were found. The D!iner initially bung the goggles 

around tbe neck. The miner had to remove the mouthpiece and noseclips to put the goggles on. After donning 

the goggles, the miner replaced the mouthpiece and 

noseclips. 

Adequatt: BCQpt worthy 

• The miner adjusted the neckstrap before activating 

the oxygen. 

• The miner adjusted the neckstrap before donning 

the goggles. After the miner put the hat 00, the miner 

fastened and snugged the waist strap. 

• The miner looped the neckstrap over the hat and 

lamp cord. 
_____ Total Time (Sees) 

Oxygen 

o 

•

s,," Hat On o Mouthpiece 

o 

Loop 

StrapS 0 	 o Noscchps 

o 

Goggles l 

___ Pan Time (Sees) 

2. 	After th~ task is completed, please list any errors thaI need to be corrected and then review these 

errors with the trai nee. 

Flgur.1.-Eval",.t:lon form tOf uHln teaching and a.usslng 3+3 donning method (4). 

I. 	Connect the dots in the diagram below to show the steps the trainee look in donning the SCSR. 

If a step was started but not finished, dip the line toward the step. Do not touch the dot if the 

step was not completed or was done incorrectly. 

Evaluation for _______________ Date _______ 

Serial Number _____ Mine _ _________________ Trial # ____ 

Tape (Y or N) 	 Type of Unit ______ 

4 
5 

Perfect: Escape worthy 

• The miner performed a perrect 3+3 sequence. 

• The miner did a perrect sequence. The waist strap 

shou1d have heen slightly tighter. 

As can he seen, failing merely applies to an individual's 

omission of one or another of the steps necessary to is0­

late the lungs. In point of fact, miners in both the failing 

and poor categories would he considered less than proficient with the apparatus. Individuals in the adequate and 

perfect categories. on the other hand, would be considered 

proficient. What the five-fold typification allows, however, 

is a generalization of the kind of errors that are being 

committed. As one reads the descriptive comments from 

failing to perfect, it can be seen that a qualitative change 

occurs in the actions that are being described. To provide 

a visual representation of the categories; figures 2 through 

6 show evaluation forms upon which several individuals' 

actual performances have been recreated. The category in 

which a particular performance falls is marked on the 

space Trial /I. These categories are: F = fail, P = poor, 

M ~ marginal, A = adequate, and PT - perfect. 

PROFICIENCY LEVELS AT EIGHT MINES 


This section presents a graphic profIle of proficiency in 

the samples at tbe eight mines in tbe study. These graphical proftles are used to illustrate and differentiate 

performance patterns within and across tbe sample. 

When looking at the pie charts in figure 7, one shou1d 

keep three factors in mind. rust, recency of training has 

a large impact on bow weU people perform. Even welltrained individuals forget things over time. Second, some 

trainers have used a modified version of the 3+3 donning 

method in their training. Therefore, that mine wou1d 

probably have no individuals in the perfect category, because perfect simply refers to a perrect 3+3 sequence. If 

the miners are well-trained, bowever, there will be many 

in the adequate category, and adequate performance is also proficient performance. Third, different mines have 

different apparatus. However, while the type of apparatus 

has been found in previous studies to be a controlling variable in predicting donning times, it has not predicted 

performance (5). With these caveats in mind, it can be 

seen that there was a significant amount of variation in the 

sample. 

Mine A, wbose safety coordinator had just trained 

everyone using the 3+3 method, exhibited the highest 

degree of proficiency. Mine C, whose miners had also 

been trained recently (within the past month), also had a 

significant number of workers who would be considered 

proficient. An interesting aspect at mine C, however, is 

the large percentage of people in the marginal category. 

This would seem to indicate that so-called secondary steps 

(such as strap adjustment and donning the goggles) either 

had not been stressed during training, or had been forgotten very quickly. Mine B, which had only 6 pet failing 

to get their lungs isolated, had a disproportionate number 

of miners who performed poorly (50 pet). One miner's 

comment, which might explain this anomaly, was that they 

were taught to do the critical steps and delay securing the 

apparatus until they were on their way out of the mine. 

The two mines with tbe highest percentage of workers who 

must be considered less than proficient were mine F (with 

only 10 pct in the adequate category) and mine H (where 

40 pct failed to isolate their lungs). 

Perbaps tbe most significant variable in determining 

miners' SCSR donning proficiency is how tbey are trained. 

There are some general principles of motor task training 

which. when applied to SCSR instruction, will yield significant resu1ts. First, prepractice instruction is very impor· 

tant. This is the point at which tbe trainee is introduced 

to the task and shown what is expected of him or her. 

Research has indicated that attention to detail at this stage 

is critical if the trainer expects his or her people to be· 

come proficient. Second, the individual learning a motor 

task (such as how to put on a SCSR) must have tbe opportunity for thorough, consistent. bands-on practice. This 

practice should be repeated until the person achieves competence. Thoroughness means that the trainee should do 

all the steps in a task, and do them properly, just as he or 

she would in an actual situation. Consistency means that 

the person performs the task the same way every time. 

Third, feedback is necessary. There is an extensive body 

of literature showing that when a person performs a motor 

task, he or she must be allowed to do the task without 

interruption. Once the task is completed, however, tbe 

individual should be given detailed knowledge of his or her 

performance. If this is not done, little learning takes 

place_ Fourth, for seldom-used motor skills (such as 

SCSR use), the person must have a periodic refresber in 

the form of practice. 

Figure 8 illustrates the points made above. It compares 

mine A, which had the highest proficiency level in the 

present sample, with a western mine (mine J) where aU 

workers were given thorough, consistent, hands-on training 

with periodic follow-up evaluations and opportunities for 

practice. 

The miners at the western site were all trained on-shift 

during production, but were nevertheless trained according 

to the motor learning principles discussed above. rlfst, 
Evaluation for _.£.11"'£"----_______ Date 1-1 - x9 

Serial Nwnber J{):5 Mine _---'1."-0_____ Trial 11_...:.'_:::__ 

Tape (Y or N) --,,1'--­

I. 	Connect the dots in the: diagram below to show the steps the trainee tOOk in donning the SCSR. 

H a step was started but not ftnished. simply dip the line toward me step. UO not touch 

the dot if the step was not completed or was done incorrectly. 

fa.'/5 Total TUn. (5",) 

Swt 

1W0n Mouthpiece 

Soaps • Noseclips 

Goggles 

_	 ___ Pan Time (Sees) 

2. 	 After the ta.S.k is completed please list any errors that need to be corrected and then com:ct 

them. 

- /?"J!PAIol# d /cJc.&.~ CJc)r PVe'1i f &:.t<tfE 5r~A'" /9/U. ;'$/""~ IV/:­

;44/ ,.,.&..( /"vr /PJ~ /MC:( .I "..J B tlr j::.<t;rr /q .r'u~ N (' g...,., « "...", 

/.1«, #AP ,;0'0.., J?1~ 5eu~ 7e-s::& __'" 77_4' 

Figure 2.--£valuatlon form lot failing performance. 

6 
Evaluation for _-,-h-,-/'.:::'!(~ ______ Date J - / ­ ?"l

Serial Number sA Mine _ -""-_____ Trial # ;J --'--­

Tape 

1. 	 Connect 

(Y or 

the 

N) 

dots 

--;

in 

;,LYthe diagram below to show the StepS the trainee took in donning the SCSR. 

If a step was staned but not futished. simply dip the line toward the step. Do not touch 

the dot if the step was nOt completed or was done incolTectly. 

I 	i 111Total Time (Sees) 

1lat0n __ 

Saaps 

---f--T--~. 

Go

•.... 

7 Z . ,Y 7 Pan lime (SetS) 

2. After the taSk is completed please list any errors that need to be corrected and then correCt 

them. 

-	 1lt4."el&~(&)OS'"(·w.A fot:.4M ~'/lcve?l"'-C'<'7~.s S/~ Thr-J/AJ~~ 

hf",!€! .:& .A.JJ~..sr4u<.J7A';9P 

- #{ hVAU.Y jJlf{'/~ ;;/.(,u,..2;;ArP/;f/ffSr_,I4,~ &~ ~/.o", r S-"OG // 

- ;#'~~#lr6-~~~.$ 

-	 $ ~et.r ;.IAj ex J";?~1!-z.7 ,A)nfe,MoIS AAW tJAI$~e e'~ACT'J' 41h'~ 

h	 . /,Ie-.dIo.c::1!!TA'U t.vl&.J&,5 IJoGAr$ 

1 
Evaluation for __~flC!....::D,-_____ Date / - / - £9 


Serial Number tZlT Mine _-'-li"-____ Trial # _~!!l=-__ 


Tape ('{ or N) --"... 1_ 


1. 	 Connect the dots in the diagram below to show the steps the trainee took in donning the SCSR. 

If a step was started but not finished. simply dip the line toward the step. Do not lOuch 

the dot if the Step was not completed (X' was done incorrectly. 

5'P. "" Tocal Time (Sec.s) 

lIMOn 

Soaps • 

Goggles 

•

Mouthpiece 

Noscclips 

Z,/ . Zl:J Pan Time (Sees) 

2. 	 After the task is completed please list any elTOl"S that need to be conected and then CQm:Cl 

them. 

Figw. 4.-£vel".tJon form for margInal p.rformanu. 

8 
Evaluation for _-<.E.--"lJ<-_______ Date 1-1-(7 

Serial Number ~7 S Mine _-I.F______ Trial # _---'-ff'--_ 

Tape (y orN) •

y 

1. 	Connect the dots in the diagram below to show the steps the trainee took in donning the SCSR. 

If a step was staned but not futished. simply dip the line toward the step. Do not touch 

the dot ifthe step was not completed or was done incomcdy. 

tJ y . {; 9 TotaJ Time (Sea) 

s"" ....On Mouthpiece 

Loop 

Noseclips 

Goggles 

3/. g'l Pan Time (Sees) 

2. 	 After the taSk is completed please liS( any errors that need to be corrected and then comet 

them. 

9 
Evaluation for_..I.@=~.L._______ Date I - I - t f 


Serial Number Zft/J Mine ---, ,---_____ Trial # __=;2'r __


Tape (Y or N) ;tJ 

1. 	 Connect the dots in the diagram below to show the steps the trainee took in donning the SCSR. 

Ifa SlCp was staned but not furished. simply dip the line toward the step. Do not touch 

the dot if the step was nO( completed or was done incom:ctly. 

'1$~ If ToW Time (Sees) 

Mouthpiece ""On 

Loop 

s ..... 

z"z. .s'~ Part Time (Sees) 

2. After the task is completed please list any errors that need to be corrected and then correct 

!hem. 

10 
11 

3.30 

pet 6.30 

Mine A Mine 8 Mine C 

Mine D Mine E Mine F 

KEY 

FOiling 

Poor 

Marginal 

Adequote

E:,'...9) Perfect 

Mine G Mine H 

Figure 7.--{)onnlng proficiency profil•• 'or umpl•••t eight min••. 

preprac:tice instruction was given individually, "";(h tbe 

trainer talking the miner through the 3 +3 procedure one 

step at a time as the worker actually put the apparatus 00. 

The complete procedure (including mouthpiece insertion) 

was taught using training apparatus equipped with quickrelease soap clamps and replaceable mouthpiece assemblies. Second, the trainee was required to practice 

donning the SCSR, without prompting. and was evaluated 

with the 3+3 evaluation form . The 3+3 evaluation form 

was tben used (0 give feedback after each trial 

performance. Third, the individual practiced until he or 

she had done five perfect sequences. Finally, the miners 

at this site were given the opportunity to practice donning 

the SCSR at least once more sometime during the year. 

Within a week after their initial training. 30 miners at 

the site were selected randomly for a follow-up evaluation. 

This evaluation followed the same protocol that was used 

for evaluating the sample in the present study. An 

examination of the graphic depicting mine A (lig. 8) at 

1 week after training and mine J at 1 week after training 
u 


shows that, even when trainers are leaching the same 

procedure (the 3+ 3), attention to tbe basic principles of 

motor task training will yield significant results.

•

Mine A at 1 week Mine J at 1 week 

3.30 

pet 

Mine J at 9 months 

KEY 

Failing 

Poor 

~~MorginOI Adequate 

"'-''-oJ Perfect 

Fig"'. L-Comparl.on of donning pt'oftclency 1 week ane, training at I'I\IM A wtth protlclency 

a' we....n mine 1 w..tI after tralnlng. 

In fact, 

these desirable outcomes bold up over time. The same 

individuals at tbe western mine, wben evaluated 

6 to 9 months later, still exhibited high levels of 

proficiency. As tbe pie chart characterizing the 9-montb 

evaluation shows, however, tbere was a significant amount 

of forgetting over time. Over balf of those who did a 

perfect sequence originally fell into one of the other 

categories, The proportion of marginal performance 

doubled, and tbere were, at 9 months, some miners who 

fell into tbe poor category. If the pattern seen at the 

western site is extrapolated to mine A. it is easy to see 

that the mine A workers, who were not trained so weU 

initially, would look much less proficient at 9 months. Tbe 

key to achieving and maintaining SCSR donning proficiency, therefore, can be summed up in one sentence: 

Train weU initially, and be prepared to offer tborough, 

consistent, bands-on practice periodicaUy. 
13 

ERROR PROFILE OF SAMPLE 


Table 1 shows the fr equency of errors made on each 

step in the donning procedure. 

Table 1.-Donnlng errora by mine 

Procedural step Mine Mine Mine Mine Mine Mine Mine Mine Mine Total 

A B C 0 E F G H J' 

Loop neekstrap 

ovlr head 

Activale oxygen ...... 

Insert mOYth pieCi .... Put on noseclip. .... . Put on goggles ...... Adjuat straps ........ 

Replace hat 

2 

0 

5 

• 

0 

,. 

0 

7 

0 

7 

7 

10 

26 

• 

2 

1 

7 

• • •

11 

1 

4 

•
• 3 

15 

3 

7 

11 

• • 12 

• 

• 2 

7 

• 15 

24 

19 

3 

• 5 

7 

7 

17 

5 

• 1 

,.

10 

3 

26 

7 

1 

3

1 

2 

10 

,

10

,.

73

59 

OS

15.


OS 

IWe.tern mine. 

Errors were not counted 

twice. Thus, if an individual made a sequencing error 

while inserting the mouthpiece, took it out, put it back in, 

but fail ed to get a good seal, the miner would only be 

credited with one mouthpiece error. By the same loken, 

if a miner made a mouthpiece error and subsequently COT

reeted it, the miner would still be cbarged with having 

made an error. Also, an individual can be represented 

more than once in this table, since it is possible to make 

an error on more tban ooe step. 

Concerns voiced early in tbe study involved questions 

regarding tbe willingness of miners to insert the mouth· 

piece during the donning trial. The reason given for the 

expected refusal was that trainers did not typically require 

insertion or the mouthpiece during rerresher training? 

­

' Moulhpiece inKnion if skipped beuU$e of roncem5 aboul Ihe 

spread of ronlagiOIl5 di5eases, Ihe efron and expcnK required 10 un itil:e 

mouthpieces, and Ihe (ael Ihal simulalion of mouthpiece jl"l$Cniol"l i5 

a«eplable unde r Ihe mandated In ining regulations. 

As 

was mentioned earlier, insertion of the mouthpiece during 

the present study was not an issue: once miners were 

assured that tbe mouthpiece assembly had been sanitized, 

tbey were quite willing to cooperate. However, most of 

the miners in the sample had periodically demonstrated a 

broken sequence. The break occurred when the miner 

would perrorm the steps up to insertion or the mouthpiece, 

tben stop, explain bow to insert, and continue with the 

remaining steps. An interesting finding. therefore, was 

tbe frequency of moutbpiece errors committed by individuals when they allempted to insert the mouthpiece. 

Mine E and mine H had the highest frequency, foUowed 

by mine D. Even mine A, where the miners had just been 

trained, had five people who made mouthpiece errors. 

Included is the sample from the western mine, where 

everyone inserted the mouthpiece as part or their training. 

as point of comparison. One person in tbis group, taught 

to do tbe complete 3+3 sequence, committed a mouth

piece error upon being evaluated some 9 months after 

training. 

Another interesting aspect of the error proftle is the 

percentage of miners in the sample who put the noseclips 

on before inserting the mouthpiece. This was done aI

tbough it is an awkward reversal of steps, and no training 

materials recommend that sequence. Table 2 shows that, 

of those who did both steps, a noticeable percentage of 

miners at mine B, mine H, mine C, and mine G made this 

sequencing error. 

­

Table 2.~ercent8ge 01 miner. who put no.ecllps on belore mouthpiece 

Mine Mine Mine Mine Mine Mine Mine Mine Mine Total 

Noseclips put on- A B C 0 E F G H J ., 

average 

Belora mouthpiece: 

Number ....... 

Pot ........ ... 0 

0 

5 

1&.1 • 21 .4 

,. 

43.8 

2 

• .0 

2 

7.1 

5 

1&.7 

•

Hi.4 

1 

3.• 

39 

15~ 

After mouthpiece: 

Number ....•.. . 

Pot .......... . 100 " 28 

83.• 

22 

78.6 

,.

56.3 

23 

"

28 

92.9 

25 

83.3 

22 

... 27 

98" 

21. 

... 
 TOlal number . 8 II l:!8 ~ 2! 28 11I l!!I a 2!' 


At mine D, almost half (43.8 pet) of the 

miners put the noseclips on before attempting to insert the 

mouthpiece. The most likely explanation for this phe

nomenon is that in hands-on training where mouthpiece 

insertion is simulated, tbe real sequence of steps is to 

activate the oxygen and then to put on the noseclips. 

Therefore, even when mouthpiece insertion is to be performed, as it was in this series of evaluations, the sequence 

stays confused ror a sizeable proportion of people. They 

are in effect omitting the mouthpiece step initially. 

­

­
14 

The problem with changing a sequence, once taugbt, is 

illustrated by an analysis of 624 SCSR donning trials conducted by tbe Bureau in 1986 and 1987. During these 

trials, there were 275 omitted steps. Oo1y 90 of the 

omissions were subsequently corrected by the iodividual in 

the process of putting on the SCSR. A logical conclusion 

is that when individuals skip a step. they usually continue 

with the donning procedure and do not go back and correct themselves. It bas also been observed that when a 

person skips a step and does attempt to correct tbe 

omission, he or she may become confused and pronc to 

error. 

Table 3 looks at the problem from a slightly different 

perspective. 

Table 3.--Pereenwge of mine,. who put 


noMelips on belore mouthpl4M:e 


and subsequently lalled 


Trained to Not trained Total 

Minerl inlert to insert 0' 

mouthpiece mouthpiece average 

Failed: 

Number .. 14 14 28 

Pet ........... 56.0 33.3 41 .8 

Isolated lungt: 

Number ........ 11 28 3' 

Pet .. , ..... ,. , 

Total number . . 

44.0

,., 

66.7 sa.2 

42 "' 

This table draws upon data taken both (rom 

177 individuals originally trained to insert tbe mouthpiece 

during Bureau research, and the 243 miners in the present 

study. It indicates the outcome for people wbo first put on 

the noseclips, and then eitber auempted to insert the 

mouthpiece or omitted it entirely. As can be seen, 28 of 

the 67 people (4l.8 pet) who initially omitted the mouthpiece step subsequently failed. 

Table 4 is related to the other three, but illustrates the 

problem of mouthpiece insertion from yet another slightly 

different perspective. 

Tsb" •.-fallures due to mouthp14M:e errors 

Trained to Not trslned Total 

Miners insert to in.ert 0' 

mouthpiece mouthpieoe everage 

Mouthpiece errors: 

Number .... , 29 38 

Pot ....... 25.0 sa.O 44.2 

Other critical errors: 

Number ......... 27 21 48 

Pet .... .. .... . . 75.0 42.0 55.8 

Total number ... ~ !!l! I!i! 

This table draws upon the same two 

data bases mentioned above, and simply shows what proportion of failures is due to mouthpiece error no matter 

what the sequence, As can be seen, a significantly larger 

percentage of all failures among the sample in which 

mouthpiece insertion is not routinely taught can be 

attributed to mouthpiece error (58 '15. 2S pct). 

In summary, table 1 merely profiles error frequency by 

mine. Table 2 indicates a tendency among a sizable proportion of the present sample to change the donning sequence by putting on the noseclips and then inserting (or 

attempting to insert) the mouthpiece. Table 3 illustrates 

tbe consequences of omitting the mouthpiece step until 

after the noseclips have been put on by showing tbat over 

40 pct of the people wbo did this subsequently failed to get 

their lungs isolated (although the reason for the failure 

varies). Finally, table 4 suggests that trouble with the 

mouthpiece is not as much a reason for failure among 

those who have originally been trained to insert tbe 

mouthpiece as among those who have not. 

SAMPLING AND QUALITY CONTROL 


The random selection of miners within each of the eight 

sites and the size of the samples (approximately 30 miners 

at each site) allow the use of probability theory to draw 

inferences about the donning proficiency of the workforce 

at each of the eight mines sampled. The inferences one 

could make from the data would concern the proficiency 

level of all miners at the site, based upon some observed 

proportion in the sample (percent failing or percent perfect for instance). 

Suppose a trainer is willing to tolerate a proficiency 

proftle at his or her mine in which 10 pet of the workers 

fail to isolate their lungs during a SCSR donning evaluation. If the mine is small, it might be possible to evaluate 

everyone who goes underground. This trainer could then 

characterize the total workforce using descriptive statistics offering an absolute profile of worker's competency in 

SCSR donning. If, however, the population of the mine is 

large, it might not be feasible to' evaluate everyone. 

Therefore, the trainer would have to evaluate a random 

sample, and make inferences about how well the statistics 

he or she uses to characterize the sample reflect on the 

population. 

Finding a 10 pct failing rate in tbe sample wouJd not 

necessarily mean that the proportiOD of failures in tbe population is 10 pct. In fact, such coincidence would be highly 

unlikely. The true proportion of all miners in the failing 

category might be S. 12, or 20 pet. The reason for this is 

that samples, no matter how carefuJ one is to use good 
15 

randomization techniques when they are drawn, seldom 

reflect all the variation that might be found in the 

population. For this reason, sample size is obviously 

important, along with a random selection of miners (giving 

aU elements of a population an equal chance of being 

selected). Both these factors help to increase confidence 

in the (}"pes of inferences one can make about the population based on performance within the sample. 

In essence, what ODe does when making inferences 

about a population based OD sample characteristics is test 

the hypothesis that there is no significant difference 

between the sample proportion (in this instance, percentage of all people in the failing category), and the 

proportion that would be found in the population if the 

entire population were evaluated. An accepted convention 

is to use the 95 pct probability figure in deciding whether 

to accept or reject this hypothesis. Outcomes are always 

either 1 or 0: a person either wins the lottery or does not. 

What the 95 pct probability figure means, however, is that 

if a person took an infinite number of random samples 

from a population and determined a proportion for each 

sample (percent failures, for instance), 95 pct of those 

observed proportions would be within plus or minus 

1.96 standard errors of the true population proportion. 

Five percent of the observed proportions would be outside 

these limits. Since 95 pct of all observed proportions will 

be within plus or minus 1.96 standard errors of the true 

population proportion, one can use this information to 

construct a confidence band around any particular 

observed proportion in a sample. 

The first step is to find the standard error of the 

observed proportion. This is done by taking the square 

rool of the observed proportion (p) multiplied by 1 minus 

the observed proportion (si nce outcomes arc always 1 or 

0) and divided by the number (n) in the sample: 

Standard Error = (p)(l-p)/n. 

The confidence limits can then be expressed as: 

Confidence Limits = p :! 1.96 «p)(l-p)/n). 

Since 95 pct of the sample proportions observed will be 

within plus or minus 1.96 standard errors of the population 

proportion, and one uses plus or minus 1.96 times the 

standard error of an observed proportion to construct a 

confidence interval around it, then 95 times out of 100 this 

confidence interval will capture the true proportion. Thus, 

there is a one in 20 chance that the true population mea n 

is outside of the confide nce band. 

It was suggested earlier that one way to increase the 

confidence in a sample is to increase the sample size. 

Increasing the sample size decreases the standard error, 

and hence narrows the confidence interval. Figure 9 illustrates a practical application of this logic. 

a: 

z 

Q 

fa: 

0 

0­

0 

CJ: 

0­

Z 

0 

f­

-' "" :0 

0­

~ 

(p.,/n) 

.S 

.7 

•• 

.5 

•• 

., 

.2 

. 1 

o . 1 I. 

OBSERVED SAMPLE PROPORTION 

Flgur. SI.-Confldence Int.",ats. 

It shows 

confidence intervals for proportions that might be observed with samples of size 30 (6). P, given on the vertical 

scale, is the true population proportion for a particular 

observed sample proportion (p = rl n on the horizontal 

scale). Suppose an evaluation of 30 miners resulted in 

nine failures. The 95 pct confidence limits for an observed 

proportion of 30 pct (shown as 0.3 on the horizontal 

scale), when the sample size is 30 (indicated by the outermost curved lines), are approximately 15 and 50 pet. Intuitively, 95 pet of all observed proportions of 30 pet, taken 

from samples of 30, and having lower limits of 15 pct and 

upper limits of 50 pet, will contain the true population 

proportion. If the person doing the evaluation i~ satisfied 

with a true failure rale of at least 15 pct, then the fa ct that 

he or she had a sample proportion of 30 pet in the failing 

category would not be unusual. 

Establishing confidence limits around observed sample 

outcomes has certain advantages for those taking a quality 

control approach to hypothesis testing. First, it divides all 

possible outcomes into two sets: those that are likely, and 

those that are not. Therefore, at the same time one rejects the null hypothesis of no significant difference between the observed sample proportion and the true population proportion, one can also make statements about 

what the parameters of some expected outcomes are likely 
16 

to be. Second, the greater tbe distance of the observed 

outcome from the confidence interval, the more clear-cut 

the choice of whether to accept or reject a hypothesis of 

no significant difference (7). 

In taking a quality control approach to SCSR donning 

proficiency. the evaluator would only be concerned witb 

whether the characteristic proportion observed in the 

sample exceeds some predetcnnined standard. In this 

case, he or she would use tbe lower confidence limit, 

because there is no interest in an observed proportion that 

might be significantly less than the standard. If, then, the 

trainer or training specialist decides that he or she will 

tolerate no more than a lO-pct failure rate at a mine. the 

(wo points of interest on the first graphic in this section 

would be the lower confidence interval (represented by the 

curved lines) and the dark borizontalline drawn at 0.1 on 

tbe vertica1 scale (representing a true population proportion of 10 pet, the standard). For a sample of 30, the 

two lines intersect at an observed sample proportion of approximately 23 pet. Anything to the left of this intersection is "within tolerance,M and anything to the right can 

be rejected witb a high degree of certainty that the true 

population proportion of failures is more than 10 pct. 

Figure 10 uses tbe procedure discussed above to show 

whicb mines in the Bureau's sample bave proportions of 

failures outside the confidence band, and therefore would 

almost certainly bave a failure rate of more than 10 pet if 

al1 workers at the operation were evaluated.

w 

u 


Z 


4 


~ Within confid '" . nce bond ~ 0_ [@ OuI.ide conf idence bol'ld 

.. 

~u 

~~ 

W 

z '" 

::; 0 

A B c D E F G H J ~ MINE 

Figure 10.-Percentage of miners failing to Isolate their lungs 

(by mine.) 

Assuming 

that samples were drawn randomly. there is still a drawback to the use of this procedure that deserves a caveat. 

While it is necessary to have a sample size of at least 30 in 

order for the sampling distribution to be normal in shape, 

there is a rule of thumb that the sample should not exceed 

S pet of the population. The reason for this is that sampling without replacement limits the number of cases available to be selected as more and more are removed from 

the popUlation (8). 

Mine A was so small that its sample of 30 constituted 

56 pet of the popUlation. With this exception, mines in the 

present study had between 9 and 14 pct of tbeir populations in the samples taken. Since the binomial distribution 

is of questionable validity when sampling without replacement from finite populations, the hypergeometric distribution was used to calculate 9S pet confidence limits for 

the mines. There was only a slight difference in outcomes: 

Mine E changed its place from within the confidence limit 

to outside it. 

Treating mine A as a special case requiring descriptive 

statistics, it was decided to focus on whether tbe quality 

control graph depicted in figure 9 could have a practical, 

though admittedly crude, application to the problem of 

trying to draw inferences about workforce proficiency 

from sample performance. While use of the binomial distribution led to wider interval ranges. the bypergeomelric 

test suggested that using the binomial would not lead to 

significant error in forecasting SCSR proficiency at the 

other mines. The point to be remembered here is tbat, 

while random sampling can allow us to make inferences 

about the population within certain limits, tbere is not a 

one-to-one correlation between what one observes in a 

sample and what one is likely to find in the population. 

DISCUSSION 


This report has suggested that sampling and evaluation 

might be used to promote competency based training. The 

confidence bands (fig. 9) can be used here, too. Suppose 

that instead of focusing upon failures, a trainer decides 

tbat his or her workforce should be competent with the 

SCSR. The usual criterion for defining competence is that 

a person must be able to do a task correctly. Again, 

following convention, he or she dctcrmines that to consider the miners competent, 90 pet ofthe population ought 

to be able to don the apparatus proficiently (fall into 

either the perfect or adequate category). Assuming a sample of 30, the trainer would locate the 90 pet true population proportion on the vertical scale (given here as 0.9) 

and locate the confidcnce intervals that would include this 

proportion 9S pet of thc time. The lower limit, reading 

across, is approximately 77 pct. Thcrefore, he or she 

would need a combined observed proportion of perfect 

and adequate performers totaling at least 77 pet to consider the workers competent. As figure 7 indicates, none 

of the eight mincs mct this criterion. There appears 
17 

to be much room for improvement if one focuses on 

donning proficiency. The error proftles for each of the 

mines (table 1) offer some specific guidance and targets 

for improvement. 

Finally, as figures 7 and 8 imply when comparing 

the eight·mine sample to the western site, it is not 

prohibitively difficult to achieve and maintain competence 

in donning the SCSR. The primary requirements are attention to detail when training, feedback or knowledge of 

results, periodic follow-up evaluations, and the opportUJ1ity 

to practice when needed. 

REFERENCES 


1. U.s. Code or Pederal Repl.tb lll. nile JO-Mineral Re5o\l~ 

OuIpter I-Mine S.fety .nd Healtb Administntion, Dep. labor, 

SlIbchipter I>-CoII Mine s.tety .nd Health; J\lI)' I, 1988. 

1. Fedenl Repter. U.s. Mine Safety . nd Health Administntion, 

(Dep. lIbor). R\lIcs . nd Repillions; Self·Cont.ined Self-Rc.scue Devicu; EmeracncyTemporary Stand.rd. V. 52, No. Ill, J\lne 30, 1987, 

pp. 24374-24380. 

3. U.s. Code of Federal Repillions. ntle 3O-Mineral Ruoum:s; 

Cr.. pter I-Mine Safety .nd Health Administntion, Dcp. Labor, 

S\lbch.pter H-Ed\lcllion .nd Tninins; P. rt 48-Tnining and 

Retnining ot Minen; J\lI)' I, 1988. 

4. U.s. Mine Safety .nd Health Administntioll (Dep. lIbor). 

Catalog of Tnining Prod\lcu for the Minin, tndllStl)'. 1980, 9$ pp. 5. Univcnity 0{ Kent\lcky. Ruurch .nd EVIIluatioa Mctbock rex 

MeaS\lring Nonroutine Mine He.lth .nd S.fety Skilk: Vol\lme 1 (COGtnct H0348OW). B\lre'\I OFR 18(1)-89, 1988, 229 PP.; NTIS PB89­

196646. 

6. Nllrell., M. Experiment.l Statistics. U.s. Department of Com-­

mem:, Nalion.1 B\lrea\l of SlIndard..5 H.ndbook, 1963, pp. S.:z.....a..21. 

7. Loelher, H ., .nd D. McTavish. InCerenti.1 Statistics tor Soci~ 

gists: An Introd\lCtion. Allyn .nd Bacon, Inc., 1974, pp. 106-134. 

8. Henry, G. Practical Sampling. Sale P\lbl. Inc., 1990, pp. 43-44.