Risk Of Airborne Transmission Research Articles

Comparing strategies for the mitigation of SARS-CoV-2 airborne infection risk in tiered auditorium venues

The COVID-19 pandemic demonstrated that reliable risk assessment of venues is still challenging and resulted in the indiscriminate closure of many venues worldwide. Therefore, this study used an experimental, numerical and analytical approach to investigate the airborne transmission risk potential of differently ventilated, sized and shaped venues. The data were used to assess the magnitude of effect of various mitigation measures and to develop recommendations. Here we show that, in general, positions in the near field of an emission source were at high risk, while the risk of infection from positions in the far field varied depending on the ventilation strategy. Occupancy, airflow rate, residence time, virus variants, activity level and face masks affected the individual and global infection risk in all venues. The global infection risk was lowest for the displacement ventilation case, making it the most effective ventilation strategy for keeping airborne transmission and the number of secondary cases low, compared to mixing or natural ventilation.

Mitigating airborne infection risks in public transportation: A systematic review

Airborne infections pose significant challenges to public transportation systems which can result in significant decline in ridership levels and financial stress for operators. This systematic review presents a comprehensive overview of measures and strategies employed by ground public transportation agencies to protect passengers and staff while ensuring the uninterrupted operation. This study also conducted a bibliometric analysis to provide insights into key topics, publication patterns, and major contributors in the field of airborne transmission research in public transportation. We have included studies published from January 2003 to June 2024, which reported measures and recommendations for managing public transportation to reduce virus transmission. Of the 2848 initially identified studies, 69 met our eligibility criteria. Our review identified four key strategies to prevent virus transmission in public transportation, including air quality improvement, cleaning, mask-wearing, and social distancing in vehicles and stations. While social distancing poses a significant challenge to public transportation, the integration of crowd management techniques and technology-driven information dissemination can provide effective strategies for managing capacity. The adoption of technology-driven solutions, such as efficient filtration systems, automated mask detection mechanisms, ultraviolet disinfection devices, and real-time passenger information, is required to implement these strategies effectively. Transportation agencies can utilize an airborne infection risk calculator during pandemics and beyond to assess and mitigate the risk of airborne transmission in various modes of transportation. Lessons from the Covid-19 pandemic underscored the need for developing advanced technologies to enhance passenger and staff safety in public transportation vehicles and stations.

Predicting the Airborne Transmission of Measles: Impact of Indoor Carbon Dioxide (CO2) Levels and Mitigation Strategies.

Measles is a highly contagious cause of febrile illness typically seen in young children. It is transmitted primarily through respiratory droplets and small-particle aerosols and can remain viable in the air. Despite the availability of an effective vaccine, measles remains a major global issue, particularly in regions with low vaccination rates. This study aimed to quantify the airborne transmission risk of the measles virus in various indoor environments. Using indoor carbon dioxide (CO2) levels, we estimated the probability of airborne transmission and the basic reproduction number (Ro) in four hypothetical indoor scenarios, including restaurants, mass gathering events, homes, and business meetings, based on the modified Wells-Riley model. The relationship between airborne transmission rates and indoor CO2 concentrations was visualized, with and without mask usage. Without masks, at an indoor CO2 concentration of 1,000 ppm, the airborne transmission rates were high in homes (100.0%) and business meetings (100.0%) and moderate in restaurants (45.6%) and live events (30.6%). By contrast, the Ro was high in audience-participatory live events (60.9%) and restaurants (13.2%), indicating a higher risk of cluster infections. In all indoor environmental scenarios, a positive linear relationship was found between the risk of airborne transmission and indoor CO2 levels. The risk of airborne transmission varied significantly across scenarios, which was influenced by various parameters, such as mask usage, quality of ventilation, conversation, and exposure duration. This model suggests that the risk of airborne transmission of measles can be easily predicted using a CO2 meter.

Evaluation of upper-room ultraviolet germicidal irradiation system for air disinfection and energy conservation in multi-patient ward

High occupancy rates significantly increase the risk of airborne transmission of respiratory infectious diseases in multi-patient wards. While increasing air supply can effectively reduce airborne transmission, it also substantially raises energy consumption. Therefore, developing low-energy methods in multi-patient wards to suppress airborne transmission is essential. This study aims to evaluate the inactivation performance of upper-room ultraviolet germicidal irradiation (UVGI) against SARS-CoV-2 virus aerosols in a typical multi-patient ward using computational fluid dynamics at different ventilation rates, as well as its energy-saving effects. Upper-room UVGI reduced the virus aerosol concentrations, with a maximum decrease of up to 159 copies/m3 in the occupied zone (zone less than 2.1 m in height) observed at 8 ACH. However, increased ventilation rates limited the inactivation performance of upper-room UVGI. Two parameters of UVGI, irradiation height and irradiation flux, had been detailly evaluated. Elevating the irradiation height of upper-room UVGI could significantly enhance the inactivation performance. Increasing irradiation height from 0.3 to 0.6 m reduced the concentrations in the occupied zone by up to 11 copies/m3, while a further increase to 0.9 m decreased the concentrations by up to 55 copies/m3. However, increasing irradiation flux could only approximately linearly enhance the virus aerosol inactivation performance of upper-room UVGI. The energy consumption evaluation of upper-room UVGI shows that UVGI activation could conserve 100 kWh per year in one multi-patient ward, with a maximum saving of 333.7 kWh. These findings provide insights into the setups strategies and the energy-saving performance of upper-room UVGI systems in multi-patient wards.

Monitoring the ventilation of living spaces to assess the risk of airborne transmission of infection using a novel Pocket CO2 Logger to track carbon dioxide concentrations in Tokyo.

We employed carbon dioxide (CO2) concentration monitoring using mobile devices to identify location-specific risks for airborne infection transmission. We lent a newly developed, portable Pocket CO2 Logger to 10 participants, to be carried at all times, for an average of 8 days. The participants recorded their location at any given time as cinema, gym, hall, home, hospital, other indoors, other outgoings, pub, restaurant, university, store, transportation, or workplace. Generalized linear mixed model was used for statistical analysis, with the objective variable set to the logarithm of CO2 concentration. Analysis was performed by assigning participant identification as the random effect and location as the fixed effect. The data were collected per participant (seven males, four females), resulting in a total of 12,253 records. Statistical analysis identified three relatively poorly ventilated locations (median values > 1,000 ppm) that contributed significantly (p < 0.0001) to CO2 concentrations: homes (1,316 ppm), halls (1,173 ppm), and gyms (1005ppm). In contrast, two locations were identified to contribute significantly (p < 0.0001) to CO2 concentrations but had relatively low average values (<1,000 ppm): workplaces (705 ppm) and stores (620 ppm). The Pocket CO2 Logger can be used to visualize airborne infectious transmission risk by location to help guide recommendation regarding infectious disease policies, such as restrictions on human flow and ventilation measures and guidelines. In the future, large-scale surveys are expected to utilize the global positioning system, Wi-Fi, or Bluetooth of an individual's smartphone to improve ease and accuracy.

AeroSense: Sensing Aerosol Emissions from Indoor Human Activities

The types of human activities occupants are engaged in within indoor spaces significantly contribute to the spread of airborne diseases through emitting aerosol particles. Today, ubiquitous computing technologies can inform users of common atmosphere pollutants for indoor air quality. However, they remain uninformed of the rate of aerosol generated directly from human respiratory activities, a fundamental parameter impacting the risk of airborne transmission. In this paper, we present AeroSense, a novel privacy-preserving approach using audio sensing to accurately predict the rate of aerosol generated from detecting the kinds of human respiratory activities and determining the loudness of these activities. Our system adopts a privacy-first as a key design choice; thus, it only extracts audio features that cannot be reconstructed into human audible signals using two omnidirectional microphone arrays. We employ a combination of binary classifiers using the Random Forest algorithm to detect simultaneous occurrences of activities with an average recall of 85%. It determines the level of all detected activities by estimating the distance between the microphone and the activity source. This level estimation technique yields an average of 7.74% error. Additionally, we developed a lightweight mask detection classifier to detect mask-wearing, which yields a recall score of 75%. These intermediary outputs are critical predictors needed for AeroSense to estimate the amounts of aerosol generated from an active human source. Our model to predict aerosol is a Random Forest regression model, which yields 2.34 MSE and 0.73 r2 value. We demonstrate the accuracy of AeroSense by validating our results in a cleanroom setup and using advanced microbiological technology. We present results on the efficacy of AeroSense in natural settings through controlled and in-the-wild experiments. The ability to estimate aerosol emissions from detected human activities is part of a more extensive indoor air system integration, which can capture the rate of aerosol dissipation and inform users of airborne transmission risks in real time.

Design of convertible patient care unit for both non-pandemic and pandemic times: Prototype, building spatial layout, and ventilation design

Convertible patient care units can accommodate non-respiratory infectious disease patients in non-pandemic times and provide isolated treatment for respiratory infectious disease patients during pandemic times. A prototype convertible patient care unit covering a floor area of 1518 m2, featuring 16 wards, and accommodating 40 beds was developed to examine the impact of building spatial layout and ventilation design on the inter-zonal airborne transmission and energy use intensity (EUI) during both non-pandemic and pandemic times. Building spatial layout referred to the presence of patient corridors and anterooms, while ventilation design referred to the location of air terminals and the calculation method of residual air volume (namely, difference between supply and exhaust airflow rates). Adding anterooms provided an 18 % reduction in pressure gradient fluctuations during door-opening events. The absence of exhaust in the medical corridor, anterooms, and wards increased contamination leakages to the patient corridors. Using the differential pressure method to calculate residual air volume was more effective in controlling the inter-zonal pressure gradient than the fixed residual air volume method. Various conversion methods resulted in an 84%–134 % increase of EUI compared to non-pandemic times, without, however, corresponding reduction in inter-zonal airborne transmission risk. The condition of adding both patient corridors and anterooms, exhaust-only patient corridors, anterooms with balanced supply-exhaust airflow rates, and differential pressure method to calculate residual air volume were effective conversion strategies to simultaneously address both the inter-zonal airborne transmission and EUI. These findings provide fundamental information for designing convertible patient care units and revising related guidelines in China.

A quanta-independent approach for the assessment of strategies to reduce the risk of airborne infection

The Wells-Riley model is extensively used for retrospective and prospective modelling of the risk of airborne transmission of infection in indoor spaces. It is also used when examining the efficacy of various removal and deactivation methods for airborne infectious aerosols in the indoor environment, which is crucial when selecting the most effective infection control technologies. The problem is that the large variation in viral load between individuals makes the Wells-Riley model output very sensitive to the input parameters and may yield a flawed prediction of risk. The absolute infection risk estimated with this model can range from nearly 0 % to 100 % depending on the viral load, even when all other factors, such as removal mechanisms and room geometry, remain unchanged. We therefore propose a novel method that removes this sensitivity to viral load. We define a quanta-independent maximum absolute before-after difference in infection risk that is independent of quanta factors like viral load, physical activity, or the dose-response relationships. The input data needed for a non-steady-state calculation are just the removal rates, room volume, and occupancy duration. Under steady-state conditions the approach provides an elegant solution that is only dependent on removal mechanisms before and after applying infection control measures. We applied this method to compare the impact of relative humidity, ventilation rate and its effectiveness, filtering efficiency, and the use of ultraviolet germicidal irradiation on the infection risk. The results demonstrate that the method provides a comprehensive understanding of the impact of infection control strategies on the risk of airborne infection, enabling rational decisions to be made regarding the most effective strategies in a specific context. The proposed method thus provides a practical tool for mitigation of airborne infection risk.

Existence of a Nonzero Worst-Case ACH for Short-Term Exposure in Ventilated Indoor Spaces

A well-ventilated room is essential to reduce the risk of airborne transmission. As such, the scientific community sets minimum limits on ventilation with the idea that increased ventilation reduces pathogen concentration and thus reduces the risk of transmission. In contrast, the upper limit on ventilation is usually determined by human comfort and the need to reduce energy consumption. While average pathogen concentration decreases with increased ventilation, local concentration depends on multiple factors and may not follow the same trend, especially within short exposure times over large separation distances. Here, we show through experiments and high-fidelity simulations the existence of a worst-case ventilation where local pathogen concentration increases near the receiving host. This occurs during the type of meetings that were recommended during the pandemic (and in some cases solely authorized) with reduced occupancy adhering to social distancing and short exposure times below 20 minutes. We maintain that for cases of high occupancy and long exposure time, increased ventilation remains necessary.

Assessing the effects of transient weather conditions on airborne transmission risk in naturally ventilated hospitals

Many UK hospitals rely heavily on natural ventilation as their main source of airflow in patient wards. This method of ventilation can have cost and energy benefits, but it may lead to unpredictable flow patterns between indoor spaces, potentially leading to the unexpected transport of infectious material to other connecting zones. However, the effects of weather conditions on airborne transmission are often overlooked. A multi-zone CONTAM model of a naturally ventilated hospital respiratory ward, incorporating time-varying weather, was proposed. Coupling this with an airborne infection model, this study assessed the variable risk in interconnected spaces, focusing particularly on occupancy, disease and ventilation scenarios based on a UK respiratory ward. The results suggest that natural ventilation with varying weather conditions can cause irregularities in the ventilation rates and interzonal flow rates of connected zones, leading to infrequent but high peaks in the concentration of airborne pathogens in particular rooms. This transient behaviour increases the risk of airborne infection, particularly through movement of pathogens between rooms, and highlights that large outbreaks may be more likely under certain conditions. This study demonstrated how ventilation rates achieved by natural ventilation are likely to fall below the recommended guidance, and that the implementation of supplemental mechanical ventilation can increase ventilation rates and reduce the variability in infection risks. This model emphasises the need for consideration of transient external conditions when assessing the risk of transmission of airborne infection in indoor environments.

Zonal demand-controlled ventilation strategy to minimize infection probability and energy consumption: A coordinated control based on occupant detection

Due to the outbreak of COVID-19, an increased risk of airborne transmission has been experienced in buildings, particularly in confined public places. The need for ventilation as a means of infection prevention has become more pronounced given that some basic precautions (like wearing masks) are no longer mandatory. However, ventilating the space as a whole (e.g., using a unified ventilation rate) may lead to situations where there is either insufficient or excessive ventilation in localized areas, potentially resulting in localized virus accumulation or large energy consumption. It is of urgent need to investigate real-time control of ventilation systems based on local demands of the occupants to strike a balance between infection risk and energy saving. In this work, a zonal demand-controlled ventilation (ZDCV) strategy was proposed to optimize the ventilation rates in sub-zones. A camera-based occupant detection method was developed to detect occupants (with eight possible locations in sub-zones denoted as ‘A’ to ‘H’). Linear ventilation model (LVM), dimension reduction, and artificial neural network (ANN) were integrated for rapid prediction of pollutant concentrations in sub-zones with the identified occupants and ventilation rates as inputs. Coordinated ventilation effects between sub-zones were optimized to improve infection prevention and energy savings. Results showed that rapid prediction models achieved an average prediction error of 6 ppm for CO2 concentration fields compared with the simulation under different occupant scenarios (i.e., occupant locations at ABH, ABCFH, and ABCDEFH). ZDCV largely reduced the infection risk to 2.8% while improved energy-saving efficiency by 34% compared with the system using constant ventilation rate. This work can contribute to the development of building environmental control systems in terms of pollutant removal, infection prevention, and energy sustainability.

Bioaerosol size as a potential determinant of airborne E. coli viability under ultraviolet germicidal irradiation and ozone disinfection

Ultraviolet germicidal irradiation (UVGI) and ozone disinfection are crucial methods for mitigating the airborne transmission of pathogenic microorganisms in high-risk settings, particularly with the emergence of respiratory viral pathogens such as SARS-CoV-2 and avian influenza viruses. This study quantitatively investigates the influence of UVGI and ozone on the viability of E. coli in bioaerosols, with a particular focus on how E. coli viability depends on the size of the bioaerosols, a critical factor that determines deposition patterns within the human respiratory system and the evolution of bioaerosols in indoor environments. This study used a controlled small-scale laboratory chamber where E. coli suspensions were aerosolized and subjected to varying levels of UVGI and ozone levels throughout the exposure time (2–6 s). The normalized viability of E. coli was found to be significantly reduced by UVGI (60–240 μW s cm−2) as the exposure time increased from 2 to 6 s, and the most substantial reduction of E. coli normalized viability was observed when UVGI and ozone (65–131 ppb) were used in combination. We also found that UVGI reduced the normalized viability of E. coli in bioaerosols more significantly with smaller sizes (0.25–0.5 μm) than with larger sizes (0.5–2.5 μm). However, when combining UVGI and ozone, the normalized viability was higher for smaller particle sizes than for the larger ones. The findings provide insights into the development of effective UVGI disinfection engineering methods to control the spread of pathogenic microorganisms in high-risk environments. By understanding the influence of the viability of microorganisms in various bioaerosol sizes, we can optimize UVGI and ozone techniques to reduce the potential risk of airborne transmission of pathogens.

Investigation of the Emission Rate of Particles when Musicians Play Wind, Woodwind, and Brass Instruments

In the context of the high risk of airborne transmission of COVID-19, the question of the production of particles while playing wind instruments is highly relevant. Therefore, in this study, 23 professional musicians played their instruments in a cleanroom in cleanroom-grade clothing. The most common orchestral wind instruments flute, oboe, clarinet, and trumpet were therefore chosen. Aerosol measurements using a laser particle counter were conducted to quantify the emission rate of respiratory particles. Orchestral excerpts as well as sustained tones in two dynamic levels were played. The emitted particles were mostly in a submicron size range. For all instruments besides the clarinet, an influence of the loudness of playing on the emission rate could be observed. The emission rates for all musical instruments were independent of the passages played. Flute and oboe showed similar emission rates but lower than the values for clarinet and trumpet. While playing a note with a small volume, the flute, oboe, and trumpet have a similar emission rate as found for speaking.

Portable Air Purifiers’ Predicted Efficacy in Mitigating Airborne Pathogen Transmission in an Office Room Featuring Mixing Ventilation

Portable air purifiers have been extensively used to improve indoor air quality and mitigate the transmission of airborne diseases. However, the efficacy of mitigation is strongly affected by the interactions between jet flows of processed air from the air purifiers and the background airflows driven by the ventilation system. Critical factors in this context include the position and capacity of air purifiers and the ventilation rate of the heating ventilation and air-conditioning (HVAC) system. These factors are investigated in this study via computational fluid dynamics (CFD) simulations and the infection probability for different scenarios is quantified using the latest airborne infection predictive model incorporating recent pathological and clinical data for SARS-CoV-2. The results show that the use of air purifiers can significantly reduce the concentration of particulate matter, thus contributing to a generally lower risk of airborne transmission. However, the position of air purifiers affects their overall efficacy remarkably. Comparatively, a central HVAC system is more efficient at removing airborne particles under an equivalent ventilation rate assuming it uses a mixing ventilation scheme.

Thermofluid dynamics and droplets transport inside a large university classroom: Effects of occupancy rate and volumetric airflow

The airborne droplets released by humans while speaking or coughing are the main sources of human-to-human contagion for airborne transmissible diseases. Due to the recent SARS-Cov2 pandemic, indoor transmission in classrooms and other environments is an interesting topic investigated by the scientific community. In this work, the thermofluid dynamic conditions and the droplet transport was analysed in a large University Classroom (UC), as a function of the inlet airflow and the occupancy rate. These parameters assume a relevant role in the design stage. However, their effects on droplet transport were not deeply investigated in the literature. Therefore, different conditions were analysed, such as: full occupancy, which represents the design condition where no social distancing is enforced; half occupancy, which is representative of social distancing; and empty UC, to be considered as a term of comparison. The main novelty of this work is related to the analysis of the combined effect of thermal plume and airflow in a large UC. The numerical model for the thermofluid dynamics simulation was validated in a previous work and the droplet emission model was retrieved from the literature. High volumetric airflow is not always beneficial for the reduction of the airborne transmission risk. An important aspect is related to the combined effect of the inlet airflow and the thermal plume, which cannot be ignored if the occupancy rate assumes a significant value. Moreover, the evacuation rate and the age of the droplets are relevant indicators to assess the cleaning time.

Exploring the potential to mitigate airborne transmission risks with convective and radiant cooling systems in an office

Based on the recognized airborne infection risk, there is a raised demand to develop innovative ventilation systems to mitigate the airborne transmission risk indoors. This paper focused on two micro-environment ventilation systems, namely personalized ventilation combined with radiant panel system (PVRP) and a local low velocity unit combined with radiant panel system (LVRP) and studied the potential to minimize the airborne infection risk. The performance was compared with a typical mixing ventilation system, where supply air is released from a perforated duct. The droplet nuclei of an infected person were simulated with tracer gas (SF6) released by a thermal breathing manikin. The effect of the heat gain (38 W/m2 and 73 W/m2), breathing pattern of the infector (exhaled via the nose or mouth), desk partition wall, and air distribution methods on the infection risk were studied. The results show the infection risk of the exposed person is around 0.5 % with micro-environment systems (42 l/s) and 0.7% (61 l/s) with the perforated duct system when the occupants remain for 102 min in the space. The higher heat gain slightly increased the infection risk (from 0.71 % to 0.81 %) with the LVRP system, but it did not have an effect with the PVRP system. The desk partition wall could reduce the infection risk only to an extent. The breathing patterns of the infector do not have any influence on the infection risk for the three studied air distribution methods.

Numerical study on the cutting off performance of a novel personalized air curtain in a general consulting ward

To mitigate the risk of airborne transmission during close patient-doctor interactions in general consulting ward, a novel personalized air curtain (PAC) system is proposed to safeguard doctors against aerosol droplets. The efficacy of PAC in cutting off the patient expiratory airflow and intercepting airborne droplets was investigated through numerical simulations that examined the impact of air supply velocity and angle. Simulation results indicate that the average concentration of exhaled pollutants in the consultation room is significantly reduced by 55%–80%. A supply velocity of 1 m/s and a supply angle of 0° result in optimal pollutant concentration. Additionally, it was observed that an increase in supply air velocity during discrete phase model (DPM) simulation corresponded with an increased suspension and deposition rate which can cause to doctor infection. This study can provide effective guidance for the design and optimization of PAC in general consulting ward to reduce exposure risk and short-range infection.

SARS-CoV-2 airborne infection probability estimated by using indoor carbon dioxide

Airborne transmission is one of the main routes of SARS-CoV-2 spread. It is important to determine the circumstances under which the risk of airborne transmission is increased as well as the effective strategy to reduce such risk. This study aimed to develop a modified version of the Wells-Riley model with indoor CO2 to estimate the probability of airborne transmission of SARS-CoV-2 Omicron strains with a CO2 monitor and to evaluate the validity of this model in actual clinical practices. We used the model in three suspected cases of airborne transmission presented to our hospital to confirm its validity. Next, we estimated the required indoor CO2 concentration at which R0 does not exceed 1 based on the model. The estimated R0 (R0, basic reproduction number) based on the model in each case were 3.19 in three out of five infected patients in an outpatient room, 2.00 in two out of three infected patients in the ward, and 0.191 in none of the five infected patients in another outpatient room. This indicated that our model can estimate R0 with an acceptable accuracy. In a typical outpatient setting, the required indoor CO2 concentration at which R0 does not exceed 1 is below 620 ppm with no mask, 1000 ppm with a surgical mask and 16000 ppm with an N95 mask. In a typical inpatient setting, on the other hand, the required indoor CO2 concentration is below 540 ppm with no mask, 770 ppm with a surgical mask, and 8200 ppm with an N95 mask. These findings facilitate the establishment of a strategy for preventing airborne transmission in hospitals. This study is unique in that it suggests the development of an airborne transmission model with indoor CO2 and application of the model to actual clinical practice. Organizations and individuals can efficiently recognize the risk of SARS-CoV-2 airborne transmission in a room and thus take preventive measures such as maintaining good ventilation, wearing masks, or shortening the exposure time to an infected individual by simply using a CO2 monitor.

Impact of thermal stratification on airborne transmission risk of SARS-CoV-2 in various indoor environments

There exist various vertical temperature gradients in different-type buildings. A holistic understanding of the impact of different temperature-stratified indoor environments on infection risk is necessary. In this work, the airborne transmission risk of SARS-CoV-2 in different thermally stratified indoor environments is assessed using our previously developed airborne infection risk model. Results show that the vertical temperature gradients in office building, hospital, classroom, etc. are within the range of −0.34 to 3.26 °C/m. In large space such as coach station, airport terminal, and sport hall, the average temperature gradient ranges within 0.13–2.38 °C/m in occupied zone (0–3 m); in ice rink with special requirements of indoor environment, the temperature gradient is higher than those in the above indoor spaces. The existence of temperature gradients causes multi-peaks of the transmission risk of SARS-CoV-2 with distancing, and our results show that in office, hospital ward and classroom, the second peak of the transmission risk is higher than 10−3 in most contact scenarios, while most being lower than 10−6 in large spaces like coach station and airport. The work is expected to provide some guidance on specific intervention policies in relation to the types of indoor environments.

Standard precautions should include 'safe ventilation' to minimise far-afield airborne transmission in health and social care settings.

Standard precautions should include 'safe ventilation' to minimise far-afield airborne transmission in health and social care settings.