J. clin. Path. (1961), 14, 32.

The cleaning of ward floors and the bacteriologicalstudy of floor-cleaning machines

J. G. BATE

From the Department of Pathology, The Princess Louise Kensington Hospital for Children, London

SYNOPSIS Current trends in ward flooring materials and cleaning methods are considered from thepoint of view of the hospital bacteriologist. Methods employed in an investigation into thebacteriological safety of a number of floor-cleaning machines are described, and some considera-tions governing the choice of vacuum cleaners for ward use are discussed.

The ward floor has long been recognized as asecondary reservoir of infection (Cruickshank, 1935).The extent to which contamination from this sourcecontributes to cross-infection is not clearly definable,though it is well known that the flora of the floor isoften found to reflect that which besets the occupantsof the beds (Garrod, 1944), and instances have beenrecorded in which it has been impossible to in-criminate any other source ofcross-infection (Rubbo,1948). The avoidance of needless air contaminationby the adoption of good housekeeping methods isbasic practice in hospitals today, and if efforts to thisend are to be rightly directed and economicallyachieved, the hospital bacteriologist must be pre-pared to advise those who have responsibility on thedomestic and administrative sides. They in their turnhave become increasingly conscious of floor-cleaningproblems as the result of labour difficulties, work-study investigations, and pressures by those com-mercially interested in floors and floor cleaning.

Information on which to base such advice is notto be found amid the usual daily reading of mostbacteriologists, and therefore the following summaryof current developments in floor materials and clean-ing methods may be found useful for reference. Thebacteriologist is often asked to advise about thesafety, from the cross-infection aspect, of vacuumcleaners and floor-cleaning machines, and lackingthe time to develop a satisfactory technique foreliciting the necessary evidence, may fall back onmethods which give results of which the accuracy isfar removed from that found in his more ordinaryinvestigations. An account is therefore given ofmethods used to study this problem in a recent in-vestigation on behalf of the Division of HospitalFacilities of King Edward's Hospital Fund forLondon, the results of which are published elsewhere(Bate, 1961).

FLOORING MATERIALS

WOOD Of the types of flooring materials that havebeen used in the past for hospital wards, probablythe most popular has been wood block or woodstrip. Such flooring is undoubtedly attractive andlong wearing, but it is porous, and the surface isbroken between the strips or blocks by crevices whichretain dust. The application of seals to these floorsinstead of polish is at present gaining popularity,though not all seals give equally satisfactory results.But there seems little doubt that these finishes will begenerally used on account of their non-slip qualities,their effective filling of pores and crevices, and theirlabour-saving potentialities. There are about 40different types of seal available at present, and theTimber Development Association has published aninformative booklet about them.' This subject is alsobeing investigated by the Division of HospitalFacilities of the King's Fund, and a report on thetrials of various seals and polishes in hospital wardswill in due course be made available.

MAINTENANCE OF SEALED FLOORS Sealed floors canbe simply maintained by vacuum cleaners or impreg-nated mops, with damp mopping occasionally toclean any unusual soiling. The life of the seal may beprolonged by the application of a suitable emulsionpolish, and this can be a factor of considerable im-portance in hospital wards, which may be in constantuse for years on end without any opportunity forrenewing the seal. Some seals are more difficult toapply than others, when the time comes for the re-newal of worn areas. Thus the hospital's initialchoice of seal should be determined not only by the

"The Timber Development Association's booklet on floor seals isknown as Information Bulletin C/IB/3, and is published by theAssociation at 21 College Hill, E.C.4.

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lasting qualities of the seal, but also by the standardof the staff available for re-applying it. It is notgenerally practicable to re-seal worn areas while theward is occupied, partly because of the smell, andpartly because of the need to shut off areas of theward while the fresh seal is drying. The worn areasare always in the busiest parts.

LINOLEUM After wood, linoleum has probablybeen the most widely used flooring material forwards, either as continuous sheet or as tiles. It issemiporous, and is often wax polished, but can beeffectively sealed to prevent the treading in of dirtand to make for easier maintenance. Non-slip, resin-emulsion polishes can be applied from time to time,as for sealed wooden floors; these need relativelylittle buffing, so that daily maintenance is confined toremoving dust with vacuum cleaner or impregnatedmop and removing adherent soiling by dampmopping with antiseptic detergent when required.

RUBBER Rubber flooring is still quite widely usedin hospitals, and it has many good qualities. How-ever, it is relatively expensive, and it seems possiblethat some of the newer types of plastic materials mayprovide as high a standard of flooring at lowercost.

PLASTIC FLOORING In more recent years, rapidprogress has been made with the development ofthermoplastic 'asphalt', vinyl asbestos, and poly-vinylchloride (P.V.C.) flooring materials. Polyvinyl-chloride in particular seems to have considerableadvantages. It has resilience and a naturally toughimpervious surface, non-slip when dry. Adjacentsheets can be welded together to give a surface whichis continuous from wall to wall. Emulsion polishescan be applied occasionally, otherwise daily main-tenance needs only a vacuum cleaner or impregnatedmop. It also lends itself particularly well to damp-cleaning and flooding techniques, which are dis-cussed below. Vinyl asbestos has rather similarproperties but cannot be welded. Thermoplastic'asphalt' tiles are cheap and hard wearing, butperhaps less suitable for wards as they are relativelynoisy and less resilient.

TERRAZZO This material is unlikely to be laid inwards to any extent, as it is hard, noisy, and unlessunderfloor heating is provided, cold. But if laid withregard to certain conditions (fall towards a gutterensured, safeguards against leakage, use of built-infurniture cantilevered from the walls and clear of thefloor) it can form the basis of a system of floor clean-ing by flooding with water from strategically-placednozzles. Such a system has been in use for six years

in the Out-patient Department of The Hospital forSick Children, Great Ormond Street, London. Inthat setting it has worked well, and it is conceivablethat the system might find an application in specialplaces, such as dressing-rooms, where the need toapply stringent cleaning methods at frequent intervalswas felt to outweigh the obvious difficulties.

CURRENT TRENDS IN FLOOR CLEANING METHODS

VACUUM CLEANING AND POLISHING The danger ofsweeping with ordinary brooms needs no mentionhere, but sweeping mops and cloths impregnatedwith dust-retaining oils have recently been introducedas alternatives to the almost universal vacuumcleaner. It is said that these are efficient sweepers thatdo not disturb floor dust, but whether they remove itas efficiently as vacuum cleaners do, and whetherthey tend to leave behind a film of oil which may intime make the floor retain dust are questions whichare not yet answered. Vacuum cleaners, on the otherhand, leave no doubt of their efficiency when theyare properly maintained. The same cannot be saidof suction polishers in their present form. One typeof these machines has rotating brushes which tendto cause centrifugal dispersal of dust unless the sur-rounding flanges are adjusted accurately to the floor.Most domestics have no idea that these flanges areanything other than buffers. The cloth dust bags arequite ineffective in retaining bacteria-carrying par-ticles (Bate and James, 1958), and though paper bagsare now fitted as well, these are not often emptied,and are frequently found to be torn and useless.So far as hospital wards are concerned, it is most

desirable that the use of floor-polishing machinesshould be reduced to a minimum, partly because ofthe noise and disturbance they cause, and partlybecause of the time it takes to carry out the polishingprocedures with these machines. In this connexion,the production of self-burnishing emulsion polishesis a welcome development that may lead to greatersimplification of maintenance routines for linoleum,rubber, and plastic floors and for sealed wood floors.These polishes are applied to the floor by spray,lambswool applicator, or similar device, and are saidto need no mechanical burnishing at all, and renewalonly at intervals of several weeks, depending ontraffic.

WET CLEANING AND DRY CLEANING Damp moppingcan be highly effective so long as the mops are keptclean and enough antiseptic detergent is used toensure effectiveness up to the end of the operation.An improvement on this technique is that of floodingand wet pickup, originating in the United States.

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This can either be part of a regular routine as asupplement to damp mopping, or reserved forterminal disinfection. After removing the furniture,several litres of an antiseptic detergent solution arepoured on to the centre of the floor and spread outto the walls by a clean mop, and subsequently driedoff by a wet pick-up vacuum cleaner. Machines ofthis kind, having a hose and nozzle, are now availablein Great Britain, and seem more convenient for thepurpose than are the ordinary floor-drying machines.Wet cleaning is damaging to a wax-finished floor,

and is not considered advisable on sealed floors ex-cept for the occasional removal of heavy soiling.Flooding is obviously impracticable on porous ordiscontinuous surfaces such as timber and linoleum,where the solution may seep through. It should bereserved for impervious surfaces such as terrazzo,welded P.V.C., or other jointless composition, thoughit has been successfully used with plastic tiles wherethese have been expertly laid with waterproofadhesive.Where wet cleaning or flooding may damage the

floor surface, it may be practicable to use a dry-cleaning technique that involves the sprinkling orspraying of an emulsion polish on to the floor,followed by the operation of an electric polisher witha nylon or steel wool pad. This method has appearedto be successful in some hospitals, and is claimed tocombine cleaning and polishing in one operation;but its bacteriological effectiveness seems to needfurther investigation.

SOLUTIONS SUITABLE FOR DAMP CLEANING AND

FLOODING The 'black fluid' phenolic antisepticsand liquor chloroxylenolis both contain soaps andtherefore have detergent as well as variable anti-septic properties, but neither is very suitable for thispurpose, the one on account of its smell, andthe other of its expense, and there is a need fora cheap, effective and persistent detergent antisepticfor floor hygiene. Two developments from the UnitedStates seem promising. Adams, Fahlman, Dube,Dube, and Read (1959) found a demonstrable anti-bacterial effect for as long as eight hours aftervigorous cleaning of surfaces with a mixture ofsodium benzene sulphonate, o-phenylphenol, andp-tertiary amylphenol. The iodophors, which aremixtures of iodine with non-ionic surface-activeagents, as well as being detergent, are said to havepowerful antiseptic effects, and to remain lethal toStaph. aureus and Salm. typhi in five minutes downto a dilution of 6 parts of iodine per million(Gershenfeld and Witlin, 1955, quoted by Sykes,1958). A solution containing 75 parts of iodine permillion has been successfully used in the floodingtechnique described above.

THE SAFETY OF FLOOR-CLEANING MACHINES

As has already been pointed out, among much thatis changing in floor-cleaning practice, the use ofvacuum cleaners for removing dust remains almostuniversal. Such machines have potentialities forspreading infection, and it is important to be surethat machines in use or under consideration for pur-chase are above suspicion in this respect. Thebacteriologist asked to report on the bacterial con-tent of the exhaust air may find it all too easy to holda culture plate in the air stream for a short time, andlater to give a report on the significance of the result-ing growth. Such a proceeding is unwise for a numberof reasons beside the absence of any standard forcomparison. Accurate sampling is governed by veryprecise conditions, none of which can be observed bythis makeshift method. Furthermore, the emergingjet is of high velocity and low pressure in relation tothe surrounding air, which rushes in from all sidesto mix with it, so that the sample must include aquantity of air which has not passed through thecleaner at all. This phenomenon, an example of theBernouilli effect, is illustrated in Figure 1.There is, in fact, no accurate method for sampling

the bacterial content of air which is moving at any-thing up to 80 miles an hour. The sampling of evenslow-moving air brings in aerodynamic problemswhich most bacteriologists will prefer to avoid.Recognition of this fact led to the conclusion that thesimplest means ofsampling the output from a numberof vacuum cleaners would be to trap the air in areservoir and hold it stationary while a sample wascollected by a slit sampler (Bourdillon, Lidwell,Lovelock, and others, 1948).

Figure 2 illustrates the apparatus, which consistsof a reservoir of approximately 20 cu. ft. capacity,made out of a 4 ft. length of heavy gauge poly-ethylene 'layflat' tube 9 ft. in circumference. Theupper end is closed by pleating and firmly tied withstring, which also suspends the bag from the ceiling.The other end is open and fixed to a stout woodenframe which can be fastened down on to the surfaceof a table which forms the base of the reservoir(Fig. 3).The slit sampler stands on this table, and is thus

inside the reservoir, the electrical leads and suctionline being carried down through airtight openings inthe table top to the air pump on the shelf below. Inuse, the reservoir frame is held down on to the tabletop by light plastic clips, strong enough to maintainan airtight joint between the surfaces, which arecovered with strips of plastic foam draught excluder,but able to release the bag if overdistended. Air fromvacuum cleaners under test fills the reservoir througha lightweight polyethylene tube 4 ft. in diameter and

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FIG. 1 Aspiration of surrounding air into the exhaust jet of a cylinder-type cleaner. On the left,the motor is stationary.

FIG.2

FIG. 3

FIG. 2. The apparatus in use, collecting exhaust airfirom a large tank-type vacuum cleaner.

FIG. 3. The table which carries the slit sampler andforms the base of the air reservoir. To the right ofthesit samipler is the opening of the collecting duct.

FIG. 4. Collection of air from a small cylinder-type vacuum cleaner.

FIG. 4

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5 ft. long attached to the metal duct leading to theinterior of the reservoir through the opening in thetable top beside the slit sampler. Into the free end ofthis bag can be tied by means of a length of rubbertubing, as seen in Fig. 2, the outlet of the largestmachine examined, the whole of a cylinder-typemachine (see Fig. 4) or of a suction-polisher, ofwhich the brushes alone remain outside. Thesequence of operations in a test run is as follows:

1 To ensure a free flow of air through themachine under test, compacted masses of dust andfluff are removed from the dust container, but dirtclinging to the filtering surfaces is not disturbed.

2 The cleaner is connected to the electricitysupply and fastened inside the receiving tube.

3 The slit sampler is loaded with a plate ofculture medium.4 The reservoir is clamped down and evacuated

of all contained air by means of a second vacuumcleaner whose nozzle is inserted through a secondopening in the table top, normally kept stoppered.

5 The cleaner under test is allowed to run fortwo minutes, driving out any residual air and anydust particles from the inside of the apparatus.6 The joint between the reservoir and the table

top breaks to allow the escape of surplus air, but asthe cleaner is switched off, the reservoir is clampeddown to hold the last 20 cu. ft.

7 A 5 cu. ft. sample is then run through the slitsampler, the switch for this being outside thereservoir.

In order to discover whether the apparatus wascapable of demonstrating the relative filtrationefficiency of a number of cleaners, some preliminaryruns were carried out on machines which could beexpected to yield air in descending grades of purityrelative to one another. An old cylinder cleaner withone layer of filtering material gave four colonies in5 cu. ft. An older domestic vacuum cleaner of thehanging-bag type gave 66 colonies in the same volumeof air, rather more than the number obtained froma sample of the air in the room. Lastly, a cylinder-type cleaner was stripped of all its filtering media,and in place of the dust bag there was fitted a clothbag made of 2 mm. mesh curtain netting. This bagwas filled with the dust from the bag it replaced. A5 cu. ft. sample of the air yielded 510 colonies. Thefouling of the apparatus resulting from these andsubsequent tests was removed by washing thepolyethylene tubes with soap and water and polish-ing with an antistatic polish.

In the actual investigation, the sequence of opera-tions described above was performed three times foreach cleaner at each test. No dirt was drawn in, toolswere detached, and the air entry kept well abovefloor level.

AIR DISTURBANCE The high-velocity jet dischargeof many vacuum cleaners has already been men-tioned, and a method was also devised to assess andcompare the extent of air disturbance caused by each.In a small room, 10 ft. by 12 ft., furnished only witha bed, locker, chair, and chest of drawers, the slitsampler without the reservoir was set up on one sideof the bed. The cleaner under test stood on the otherside, between the bed and the window. To eliminatedisturbance due to suction, the end of the hose washung out of the window, the resulting gap beingfilled with broad adhesive tape. The operator sat atarm's length from the sampler, moving only as muchas was necessary to change plates, having switches athand to control both the cleaner and the sampler.After allowing 15 minutes for disturbance due tosetting up the apparatus to subside, a 5 cu. ft. sampleofroom air was taken. The cleaner was then switchedon for four minutes, switched off and a secondsample of room air taken. Six further samples weretaken at intervals of 15 minutes during the period ofone and a half hours from the operation of thecleaner. Colony counts demonstrated the degree ofair disturbance, and its subsequent settling.

CHOICE OF A VACUUM CLEANER The results obtainedby these methods have been fully reported elsewhere(Bate, 1961) and need not be repeated here, but inthe light of this work it is possible to make somesuggestions as to the choice of vacuum cleaner forward use. The first consideration should -be themethod of finally disposing of the collected dust, andpreference should be given to those machines inwhich a disposable paper bag is provided for thispurpose. Secondly, performance figures should bestudied; they are readily available. A high rate of airdisplacement is desirable; a high closed vacuum isless important, but the most satisfactory index ofperformance is the figure for suction power,measured in foot-pounds per second according to aformula laid down by the British Standards Institu-tion (1958). This is now available for most cleaners.Filtering efficiency may be considered adequate ifthere are not less than two layers of filtering materialactually within the body of the machine, on the inputside of the air impeller, and separate from oneanother so that failure of the first layer is immediatelyapparent on inspection of the second. Finally, theexhaust jet should be well diffused, and any diffusingdevice should preferably form an integral part of themachine, or be detachable only with difficulty.

I am very much indebted to Mr. M. C. Hardie, of theDivision of Hospital Facilities of King Edward's HospitalFund for London, for putting at my disposal a very largeamount of information about floors and their cleaning.

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The slit sampler used in the investigation was lent to meby the Wright-Fleming Institute of Microbiology, St.Mary's Hospital, to which I am most grateful; as also toProfessor R. E. 0. Williams for his helpful criticisms.

REFERENCES

Adams, R., Fahlman, B., Dube, E. W., Dube, F. J. C., and Read, S.(1959). J. Amer. med. Ass., 169, 1557.

Bate, J. G. (1961). Lancet, 1. To be published.-, and James, U. (1958). Ibid., 2, 713.Bourdillon, R. B., Lidwell, 0. M., Lovelock, J. E., and others. (1948).

Spec. Rep. Ser. med. Res. Coun. (Lond.), No. 262.British Standards Institution. (1958). Electric Vacuum Cleaners for

Use in Hospitals, (B.S. 3028: 1958).Cruickshank, R. (1935). J. Path. Bact., 41, 367.Garrod, L. P. (1944). Brit. med. J., 1, 245.Gershenfeld, L., and Witlin, B. (1955). Soap, 31, (12), 189.Rubbo, S. D. (1948). J. Hyg. (Camb.), 46, 158.Sykes, G. (1958). Disinfection and Sterilization. Spon, London.

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