Home › magazine › special features › Potential for contamination?
Potential for contamination?15th of June 2010
In every building on any day of the week cleaners use commercial vacuuming equipment. Many of these units are dry vacuums fitted with special filtration to control dust emissions from the vacuum exhaust which, we all know, is essential to prevent exposure of the cleaners, building workers and visitors to the hazards of fine particulates in the indoor air. The question therefore arises, if we are so concerned about the emissions from dry vacuums, why are we not concerned about atomised particulates from wet vacuuming - asks Brian Clark of Janitech.
Wet vacuuming or water pick-up devices include wet vacuums, floor scrubber dryers and carpet extraction machines. They utilise vacuum motors, or air pumps, to lift wastewater from the floor and into a waste tank. The standard vacuum motors used in these machines can pump over 45 litres of air per second, or the equivalent of the air in a 10 cubic metre room cycling through the system every four minutes, and some units utilise two or more vacuum motors to increase performance. The common denominator with this equipment is that the exhaust air is nearly
Studies from the dental industry show that airborne water droplets can stay suspended for extended periods. One publication advises that aerosols generated by rotary instruments produce airborne particles, which vary greatly in size from 0.001 microns to 10,000 microns and that aerosols consist of small airborne particles of less than 10 microns that are capable of remaining in the air for several hours and of travelling on air currents for long distance. What raises concern for this industry is the statement that contaminated aerosol can be inhaled into the respiratory passages or deposited on the skin, or the mucous membranes of the eyes and mouth (i).
The diseases caused by indoor bioaerosols fall into two categories: hypersensitivity diseases and infectious diseases (ii). In order for microorganisms to release indoor bioaerosols they must get indoors, grow and multiply on some material and then get into the air. Dirty floors, detergent residues and the warm, wet humid recovery tanks of portable cleaning machinery provide the perfect environment while powerful air pumps (vacuum motors) provide the ideal method for building contamination. It is easy to imagine the enormous volumes of aerosols that are generated daily in buildings by scrubber dryers, wet vacuums and carpet machines that have the potential to ride the air currents in the HVAC system for hours.
Infection by inhalation
This brings in another potential concern – Legionella. According to literature, many hospital and commercial hot water systems are colonised with legionellae, which is introduced into institutional water distribution systems from public/municipal water systems (iii). It is well documented that infection with L. pneumophila is caused by inhalation of contaminated aerosols (iv). Identified sources include air conditioning HVAC systems, humidifiers, foggers, water misting systems, spray humidifiers, air washers and wet scrubbers, eye wash showers, sprinkler and hose reel systems, lathe and machine tool coolant systems, horticultural misting systems, indoor fountains and water features and specialist equipment (v). And last of all - and possibly the area which has
been researched the least – commercial cleaning equipment.
In 1997 the US CDC reported that a legionella variation, Lp-6, was cultured from samples obtained from various sources, including a carpet cleaning unit (vi). This discovery was part of an extensive search for the source of nosocomioal Legionnaires disease infections that had persisted in two US hospitals between 1987 and1996. While the hot water systems in the hospitals were identified as the source of the organisms, the disturbing implication is that the carpet cleaning unit may have been a contributing factor in spreading the infection.
Design still the same
The design of wet extraction systems in commercial cleaning equipment has barely changed in 100 years. The airflow is used with specialist floor tools, detergent and warm water to release contaminants, including food spills and human waste, from flooring and to collect the residue in a sealed recovery tank, which is regularly emptied but rarely cleaned, disinfected or allowed to dry. The corrugated extension hoses used with much of this equipment are wound up and stored, usually without rinsing, with excess liquid collecting in the lower corrugations, ready to be released after a period of incubation between uses.
Vacuum motors risk
The most important component for bio-aerosol generation and contamination is the vacuum motor(s). These are powerful fans, spinning at high speeds, atomising collected waste into large numbers of tiny droplets that are forcefully ejected through the exhaust port of the machine. The exhaust port is usually a straight route out of the side of the machine, conveniently at desk level, or directed downwards onto the floor under the machine. Disturbingly, on the majority of these machines there is little or no provision for filtration or ability for end-users to adapt filters to match the enormous amount of moist airflow.
Manufacturers of these machines should carefully consider the potential for infection and environmental contamination from unfiltered wet exhaust units and take the matter in hand with future designs. Users of wet pick-up equipment should also carefully consider selection criteria including the availability of suitable exhaust filtration and the ease and accessibility of the waste tanks for cleaning and air drying between usages. In especially sensitive environments it may be necessary to develop risk management strategies to minimise the potential for this highly mobile equipment to become a source of indoor contamination with potentially infectious organisms or consider alternative cleaning methodologies.
To contact Brian Clark: http://www.janitech.com.au
(ii) Indoor Bioaerosols New Jersey Dept of Health and Senior Services Revised March, 1997
(iv) LEGIONELLOSIS RESPONSE PROTOCOL FOR NSW PUBLIC HEALTH UNITS NSW Health Revised September 6 2004
(v) http://www.admin.ox.ac.uk/safety/UPS0707.shtml Appendix 1
(vi) Sustained Transmission of Nosocomial Legionnaires Disease -- Arizona and Ohio. Morbidity and Mortality Weekly Report May 16, 1997 / 46(19);416-421 Center for Disease Control and Prevention
•We would appreciate readers' feedback to Brian Clark's findings - whether it be from users or vacuum manufacturers. Email firstname.lastname@example.org