We built a simple unipolar positive corona charger and tested it with five different medical face masks. Charging the particles significantly enhanced the filtration efficiencies of all of the masks ...in terms of the submicron fraction, with an average increase of from 58 to 93% for 0.3 μm particles. Simultaneously, the pressure drop remained practically the same, showing the high potential in using electret media. However, the corona discharge generated ozone, which is an issue that must be addressed. These results contribute to the development of effective solutions against airborne threats.
International and national travelling has made the rapid spread of infectious diseases possible. Little information is available on the role of major traffic hubs, such as airports, in the ...transmission of respiratory infections, including seasonal influenza and a pandemic threat. We investigated the presence of respiratory viruses in the passenger environment of a major airport in order to identify risk points and guide measures to minimize transmission.
Surface and air samples were collected weekly at three different time points during the peak period of seasonal influenza in 2015-16 in Finland. Swabs from surface samples, and air samples were tested by real-time PCR for influenza A and B viruses, respiratory syncytial virus, adenovirus, rhinovirus and coronaviruses (229E, HKU1, NL63 and OC43).
Nucleic acid of at least one respiratory virus was detected in 9 out of 90 (10%) surface samples, including: a plastic toy dog in the children's playground (2/3 swabs, 67%); hand-carried luggage trays at the security check area (4/8, 50%); the buttons of the payment terminal at the pharmacy (1/2, 50%); the handrails of stairs (1/7, 14%); and the passenger side desk and divider glass at a passport control point (1/3, 33%). Among the 10 respiratory virus findings at various sites, the viruses identified were: rhinovirus (4/10, 40%, from surfaces); coronavirus (3/10, 30%, from surfaces); adenovirus (2/10, 20%, 1 air sample, 1 surface sample); influenza A (1/10, 10%, surface sample).
Detection of pathogen viral nucleic acids indicates respiratory viral surface contamination at multiple sites associated with high touch rates, and suggests a potential risk in the identified airport sites. Of the surfaces tested, plastic security screening trays appeared to pose the highest potential risk, and handling these is almost inevitable for all embarking passengers.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We estimated the hourly probability of airborne severe acute respiratory coronavirus 2 (SARS-CoV-2) transmission and further the estimated number of persons at transmission risk in a day care centre ...by calculating the inhaled dose for airborne pathogens based on their concentration, exposure time and activity. Information about the occupancy and activity of the rooms was collected from day care centre personnel and building characteristics were obtained from the design values. The generation rate of pathogens was calculated as a product of viral load of the respiratory fluids and the emission of the exhaled airborne particles, considering the prevalence of the disease and the activity of the individuals. A well-mixed model was used in the estimation of the concentration of pathogens in the air. The Wells-Riley model was used for infection probability. The approach presented in this study was utilised in the identification of hot spots and critical events in the day care centre. Large variation in the infection probabilities and estimated number of persons at transmission risk was observed when modelling a normal day at the centre. The estimated hourly infection probabilities between the worst hour in the worst room and the best hour in the best room varied in the ratio of 100:1. Similarly, the number of persons at transmission risk between the worst and best cases varied in the ratio 1000:1. Although there are uncertainties in the input values affecting the absolute risk estimates the model proved to be useful in ranking and identifying the hot spots and events in the building and implementing effective control measures.
•A relatively simple but scientifically sound model for transmission of airborne infectious pathogens is presented.•This model has been applied to a real-life building and activities in a day care centre for the transmission of SARS-CoV-2.•Significant differences in infection probabilities and number of persons at risk between spaces and events were revealed.•Ranking of high-risk rooms and activities enables an efficient focus on the risk mitigation measures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of enhanced filtration on protection citizens staying indoor against airborne radionuclides released during nuclear core melt accidents was determined by field measurements using outdoor ...particles as simulants. An electrically enhanced filter was installed in the HVAC system of an office building and its removal efficiency for particles was altered by using a separate particle charging section in power on and off positions. The effect of air filtration on indoor particle concentrations was determined by using an automated measurement system which was continuously sampling from the outdoor air, filtered supply air and exhaust air. With the aid of the measured outdoor and modelled indoor concentrations the indoor/outdoor ratio of particles of outdoor origin could be accurately determined. External charging of the particles increased the electret filters removal efficiency for 0.4 µrn size particles from 60% to 95%, resulting in decrease of the average I/O ratio of the same size particles from 0.67 to 0.40. Despite the high improvement in the supply air filtration efficiency the indoor concentrations decreased only modestly which is likely due to the leaky construction of the building, demonstrating the detrimental effect of air infiltration on the protection provided by buildings against outdoor airborne hazards. Practical implications: The developed method allows quantification of the key parameters affecting the protection of buildings against outdoor contaminants, thus allowing accurate estimation of size resolved indoor to outdoor ratios for fine particles. The electrically enhanced filter can remove effectively also submicron particles thus reducing the occupant exposure to outdoor hazardous or harmful materials. Best results can be achieved with airtight buildings.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A novel method for determining air infiltration for mechanically ventilated buildings is presented in this paper. It consists of a model that uses size-resolved particle concentrations of the ...outdoor, filtered supply, and exhaust air as input. Based on these continuously measured concentrations, the infiltration rate can be inferred by fitting the experimentally obtained indoor concentrations with theoretically calculated values. The approach was validated by continuous long-term field measurements made over a four-month period. The results show that infiltration rates could be reliably estimated using this method and that the calculated infiltration rates were clearly dependent on the wind speed.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Mass transport systems are vital for big cities and their disruption may have severe consequences for the economy, safety and security of the general public. Thus far, the attacks on mass transport ...have been about twice as lethal as terrorist attacks overall. Mass transport systems are typically of open design layout with multiple access points, and these characteristics make the process of screening challenging. Therefore, the early identification of an attack plan is the most efficient way to protect such systems. This paper aims to better understand the attack phenomenon and to develop a new approach for the systematic identification of possible weak signals and their sources. If such weak signals can be timely detected and correctly interpreted, this could improve awareness and thus possibilities for intervention. The developed approach is demonstrated by applying it to two well-known but different cases: the Tokyo sarin attack of 1995 and the 2005 London bombings.
•An attack scenario model to better understand the phenomena involved in an attack•An attack scenario based systematics for identifying weak signals and their sources•Demonstrating the applicability of the proposed approach by analysis of two attacks
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Sudden large scale outdoor releases of toxic materials may require protective actions in the affected areas, and one option is to shelter indoors. Mechanically ventilated buildings provide protection ...against outdoor hazardous particulate materials with varying efficiency depending mainly on the properties of the HVAC system of the building, air leakage, and the nature of the outdoor release. A tool for modelling the indoor concentrations due to outdoor contaminants has been developed and presented. The tool solves numerically the simplified mass balance equation describing the size-resolved behaviour of airborne particles and uses as input experimentally obtained data on particle concentrations outdoors, in the supply air, and indoors. By eliminating the effect of indoor sources the size-resolved indoor/outdoor (I/O) ratio for fine particles can be determined accurately, thus giving detailed information on the buildings protective capability and thereby quantitative knowledge to support emergency managers decision making.
•Validated model for size-resolved indoor particle concentration calculation.•Method for accurate determination of buildings sheltering efficiency against outdoor pollutants.•Advanced wireless indoor air quality measurement system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
BackgroundThe shortage of FFP2 and FFP3 respirators posed a serious threat to the operation of the healthcare system at the onset of the COVID-19 pandemic.AimOur aim was to develop and validate a ...large-scale facility that uses hydrogen peroxide vapour for the decontamination of used respirators.MethodsA multidisciplinary and multisectoral ad hoc group of experts representing various organisations was assembled to implement the collection and transport of used FFP2 and FFP3 respirators from hospitals covering 86% of the Finnish population. A large-scale decontamination facility using hydrogen peroxide vapour was designed and constructed. Microbiological tests were used to confirm efficacy of hydrogen peroxide vapour decontamination together with a test to assess the effect of decontamination on the filtering efficacy and fit of respirators. Bacterial and fungal growth in stored respirators was determined by standard methods.ResultsLarge-scale hydrogen peroxide vapour decontamination of a range of FFP2 and FFP3 respirator models effectively reduced the recovery of biological indicators:
and
spores, as well as model virus bacteriophage MS2. The filtering efficacy and facial fit after hydrogen peroxide vapour decontamination were not affected by the process. Microbial growth in the hydrogen peroxide vapour-treated respirators indicated appropriate microbial cleanliness.ConclusionsLarge-scale hydrogen peroxide vapour decontamination was validated. After effective decontamination, no significant changes in the key properties of the respirators were detected. European Union regulations should incorporate a facilitated pathway to allow reuse of appropriately decontaminated respirators in a severe pandemic when unused respirators are not available.
The aim of the study was to find out good practices for effective air distribution inside a complex shaped asbestos enclosure and for control of pressure differences between the enclosure and the ...surroundings. In addition, sufficient pressure difference for asbestos containment was tested. The effect of air distribution was studied in laboratory conditions by constructing an L-shaped asbestos enclosure and connecting it to a negative pressure unit. The efficiency of six different ventilation configurations was compared using a tracer decay method and the local air change indexes as the performance indicator. The sufficient negative pressure for containment was assessed by simulating person traffic to and from the enclosure and recording the pressure difference continuously. The effect of a pressure controller unit in maintaining the target pressure difference was also tested by simulating filter loadings of the negative pressure unit causing changes in the air flow rate. The results showed that high nominal air change rates alone do not guarantee good air distribution. Effective air distribution within an asbestos enclosure can be arranged by locating additional air supply openings far away from the air exhaustion point, using recirculation air with a pressure controller, or extending the exhaust location to the poorly ventilated areas. A pressure difference of at least -10 Pa is recommended to ensure a sufficient margin of safety in practical situations.
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