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Canadian Hospital, 35, 4, pp. 46-48, 1958-06-01
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A Study of conductive flooring for safety in the O.R.
Sereda, P. J.
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- L I B R A R Y .
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N A T I O N A L R E S E A R C H C O U I { C I L
TECHNICAL
PAPER
NO. 52
Ser
THl
N21t2
n o . 5 2
e . 2
BI;DG 1
NATIONAT
RESEARCH
COUNCIT
CANADA
DIVISION
OF BUITDING
RESEARCH
A STUDY OF CONDUCTIVE
FLOORING
FOR SAFETY
IN THE O.R.
by
P. J. SEREDA
REPRINTED FROM THE CANADIAN HOSPITAT
OF THE
DIVISION
OF BUILDING
RESEARCH
Ollowq
J U N E
I 9 5 8
A
ITHE problem of safety in hos-I pital operating rooms, particu-Iarly in reference to conductive flooring, was brought to the atten-tion of the Division of Building Research by a firm of architects in 1953. Since that time. this Divi-sion and the DiviDivi-sion of Radio and Electrical Engineering have been working on the problems of safety in hospitals and, in particu-lar, on the r6le of conductive flooring in achieving safety.
It is important to stress the necessity of considering safety as a whole. All the individual meas-ures which constitute safety must be given their proper significance; even in a discussion of conductive flooring we must not over-empha-size one particular measure. One link does not make a chain, and one safety measure does not con-stitute safety.
The Danger
About 120 explosions occur in operating rooms annually in the United States, with about 30 fatal-ities. Statistics are not available f for Canada, but the explosions do I occur. Since surveys in the United States and Britain reveal that a large percentage of these explo-sions are caused by electrostatic sparks, the hazard may be even more acute in Canada. Here the humidity is lower, especially in the winter months when outside air at very low temperatures is heated as it comes into the buildings.
The hazard exists because anaes-thetic gases such as ether, cyclo-propane, and ethylene are used. These, when combined with oxy-gen, form mixtures that can be readily ignited by an electro-static spark. It has been said that "there is probably no combination of equipment and personnel activ-ity anywhere more likely to produce casual, dangerous charges of static electricity than that found in the present anaesthetizing areas of most hospitals"'. To have an ex-plosion one must have both the anaesthetic gas mixture and the electrostatic spark. Since we can-not do without the gas mixture, we must ]earn to avoid electro-static sparks.
Electrostatic sparks occur when an electrostatic charge is
neutral-1. for ref et'ences see fi.nal page.
A study of
Conductive Flooring
for
Safety in the O.R.
P. J. Sereda. Ottawa, Ont.
ized. The charge is produced by frictional movement followed by separation of two surfaces that are good electrical insulators. Non-conductive shoes scuffed on noncon-ductive floors, for example, pro-duce charges. Similarly, a wool blanket removed quickly from a table covered by sheet rubber can generate a charge. Most of the new synthetic fabrics, ordinary rubber, sharkskin, and wool pro-duce charges readily.
This charging'can be prevented if insulating materials are replaced with conducting materials. If this cannot be dqne completely, the most effective way of p_reventing electrostatic charges is by inter-connecting all objects and persons in a given area through a path of low electrical resistance. A con-ductive floor serves as a base for achieving this intercoupling to prevent charges being accumulated. The conductive floor alone, how-ever, will not achieve this because to maintain electrical continuity the shoes, casters, and leg tips must make good contact with the floor. Making the floor conductiae seroes no useful purpose, unless the surfaces touching that floor haae also been made conductiae. This fact cannot be over-emphasized.
To Be a Conductive Floor In the first place, all conductive flooring must meet the require-ment of electrical conductivity. This is designated at the present time by the National Fire Protection Association" as being one megohm, measured in accordance with a designated test. In addition, the floor must not have nonconducting
areas exceeding tlr-inch in one dimension. A nonconducting floor having a metal grid of any dimen-sions is not a satisfactory con-ductive flooring. The minimum re-quirements for a conductive floor are now being reviewed by the Committee on Hospital Hazards of the Canadian Standards Associa-tion.
The electrical resistance of any given floor, when measured in the preseribed manner, represents the contact resistance as well as the volume resistance of the material. The presence of any insulating material such as dirt, talc, or wax will show up in the increased re-sistance of the floor; it can even make it nonconducting. It is most important that all conductive floor-ing is maintained in such a man-ner that its conductivity is not affected. How this should be done will depend on what type of work is being done in the particular operating room, but the correct procedure for maintenance should always be followed.
Most conductive floors can be classed into three general cate-g o r i e s :
t. Floor Couerdngs-factory-pro-duced materials in sheet form which are bonded, usually with an adhesive, to a suitable floor or sub-floor. These include rubber, lin-oleum, and plastic material in the usual /s-inch thicknesses.
2. Floor Coatings - materials that are applied by bruph or trowel on top of an existing floor or subfloor. They consist of a var-iety of ingredients compounded to yield the desirable properties.
3. Cast-in-s,itu flooring -. mat-erials that are cast on a prepared underbed and consist of marble aggregate or ceramic tiles in a
-
: v
cementitious matrix. They are best laid during the construction of the building.
Basically these various types of conductive floorings are similar to the respective nonconductive var-ieties. Although these various types of floorings differ greatly, yet it must be remembered that we ex-pect that they will all serve the same purpose. Is it any wonder that we are sometimes disap-pointed ?
People often ask which is the best type of conductive floor. There is no simple answer to this ques-tion. In reply another question should be asked-"Which of the many requirements for a floor do you consider the most important?" As a result of the NRC study of the properties of different con-ductive floorings, we have at-tempted to rate them relative to each other on the basis of the desirable characteristics. This rat-- ing is based largely on personal
judgment. Much of the work was
done on small samples procured in 1954, and may not represent similar materials made at present. Table I presents the information gained from these investigations. Copies of the report of this study are available'.
The following remarks may help to clarify the table. Along the top are the characteristics which served as the basis for comparison. Those characteristics having to do with appearance and durability, comfort, and electrical resistance should be noted. Ease of cleaning implips that the floor must present an ac-ceptable appearance with normal maintenance. Indentation and wear refer to the ability of the flooring to resist the normal use to which it is put. Factors affecting the comfort of a person on a given fl661-1vs1's1th, quietness and non-slipperiness-are related to the property of resilience of the floor. It can be seen that the group of materials which rate high in desirable properties for service
Table I
Comparison
of Conductive
Floor Finishes Commercially
Available in 1954
rate low in the properties relat-ing to comfort. The reverse is also true.
The property of electrical re-sistance is reported for two con-ditions-when the floor is dry and when it is wet. It should be noted that the resistance of some floor-ing materials is greatly affected by moisture on the surface. Since the resistance is usually lowered by moisture, this improves static dissipation. The provision of an electric path of low resistance to ground not only reduces the danger of electrostatic sparking, but it . creates a hazard of possible elec-trical shock from faults in power circuits. This can result in shock to either staff or patient; it can even result in disaster if a surgeon is induced to make an unPlanned incision. To guard against this hazard from shock, the lower limit of the floor resistance should be maintained above 25,000 ohms. When floors do not provide this measure of safety, one must rely
Appearance and Durability Comfort
Warmth to touch Quietness Electrical Resistance Resistance to indentationj Non-slip
properties conditionsIdeal
Extremo conditions Conductive Material Cooerings vinyl tile rubber Iinoleum Coati.ngs No. I No. II No. III Cast-in-s'itu Flooring ceramic tile I ceramic tile II carbon tet:tazzo Ease of Cleaning G P F-G black with
white and green marble pattern black black to gray shiny black brown, gray, green flat black dark brown dark brown with green pattern white chips, dark gray matrix G F P F-G P-G F-G G G P-F VG-G P-F P-F G-VG G G F-G F-G G G G G G G P P G G VG G F G F-G P F G G G G P G VG VG F-G F-G VG G G VP VP GG VP F-G G F-G P
Symbols: VG-very good; G-good; F-fair; P-poor; VP-very poor.
Ease of Cleaning: The assessment includes dirt retention, the frequency of maintenance required to maintain the original appearance, and the effort required in that maintenance.
Besistance to Ind,entatioz.. This refers to resistance to permanent denting caused by furniture.
Resistance to Wear: This column assesses the performance in use at the end of 18 months of foot traffic.
Qui,etness: By quietness is meant the absence of noise nuisance produced on the occupants by their movements within the room.
Electrical Resistance: The column under extreme conditions assesses the change in resistance when the surface of the floor is wetted with water.
,F
;rF
ba
-- on first-clas_ .ctyical installations 7- which are maintained in the best
of conditions.
It is vitally important to main-tain electrical equipment in good condition, since it can be an igni-tion source for anaesthetic gases as well as cause electrical shock. This note of caution is included because it is known that electrical wiring and equipment in many in-. stitutions is in need of renair.
Maintenance
The maintenance of conductive ' floors involves the use of deterg-ents, germicides, and preservatives. Each of the products clammering to be used is advertised as being the best, but not all of these prod-ucts are the best. Sorne of them actually produce uirdesirable effects on conductive floorings. Since so many products are involved that detailed information cannot be given here, we urge you to be cautious with untried products. It may even be prudent to check the performance of the products now being used. Some germicidal agents in solution with water be-have as an acid, others as an alkali. The conductive properties of both linoleum and terrazzo are readily affeeted by such solutions.
Conductive floors can be made nonconductive by faulty mainten-ance. In one instance, a conductive tettazzo floor was made nonconduc-tive by the use of a mop which had
been used on waxed floors. Al-though there are some waxes that can safety be used on conductive floors, it is wise to obtain all nec-essary information if any conduc-tive flooring requires preservaconduc-tive treatment.
A routine check should be made of conductive flooring to make certain that your treatment and maintenance are s a t i s f a c t o r y. Simple and inexpensive test equip-ment is available for this and also for checking how effectively all objects are interconnected to the floor.
Safety Education
Safety depends on the constant vigilance which arises from an awareness acquired through educa-tion. One way of attaining it would be through instruction clas-ses in safety for the staffs of hos-pitals. Experimentation can reveal the causes of accidents that occur in hospitals and codes can be writ-ten which will recommend what can be done to prevent them from hap-pening. But unless all hospital staff, including doctors and nurses, are made aware of the whole idea of safety, accidents will continue to happen.
Where safety devices are not pfovided, as in many of the older hospitals, many simple measures can be taken. On dry days at-tempts should be made to intro-duce some humidity by any means possible, such as wetting the floors.
-All rapid motion should be slowed so that electrostatic charges are not as readily generated. Every hospital should be equipped with a static indicator. From this staff members can flnd out for them. selves which of their actions pro-duce the most charges. Then those activities and materials that pro-duce an electrostatic hazard, should be eliminated. Even without any of the special safety devices which can minimize the hazard of hos-pital operating room explosions, accidents would be reduced if every member of hospital staffs were informed and cautious. Although the National Research Council realizes the importance of these problems and will continue work-ing in this field, no amount of research can ensure safety in oper-ating rooms of hospitals. The re-sponsibility for this must rest with hospital personnel.
References
1. Guest, P.G., V. W. Sikora, and B. Lewis: Stati,c electrici.tg in hospi,tal operating suitas. U.S. Bureau of Mines, Bulletirr 20.
2. Sereda, P. J.: Properties of comtizercial conductiue floori,ng f or Itospital operati,ng roonxs. Pp. 17. August 1956. NRC 4031.
3. Recommended safe practice f or ltospital operati.ng . roonls. N.F.P.A. No. 56 of the National Fire Protection'Association. Bos-ton, Pp. 40.
