Scientific publications

The respiratory system is equipped with several defence mechanisms to protect the body from microorganisms and airborne pathogens. There are situations where the respiratory system can be overwhelmed or compromised and infection happens, especially in individuals with weakened immune systems. Airborne pathogens are a serious risk for human and animal health, as exemplified by the challenges faced during the COVID-19 pandemic. The list includes viruses of varying severity such as Influenza virus, SARS-CoV-2, measles virus, Varicella-Zoster Virus, or Respiratory syncytial virus among others. Smaller particles can remain suspended in the air for longer periods and may reach the lower respiratory tract, including the alveoli in the lungs. The real-time detection of these pathogens in the air presents a significant challenge. The aerosols, especially those carrying viruses, are so small that they often elude conventional air samplers, making it difficult both to detect their presence and to remove them effectively from the air. This work introduces a recent technique designed for rapid aerosol sampling, with a particular emphasis on virus sampling. The system underwent calibration using artificial F29 virus aerosols and was subsequently tested with naturally emitted aerosols of SARS-CoV-2. A series of tests were conducted in diverse settings, including hospitals, farms, offices, and railway cars. The equipment is also capable of swiftly removing bioaerosols from the air, thereby facilitating effective decontamination. The relevance of this technology lies in its capability for swift detection and elimination of viruses and other kinds of aerosols from air, facilitating prompt decision-making during high-risk events.

The experience of COVID19 pandemic has demonstrated the real concern of biological agents dispersed in the air and surfaces environments. Therefore, the need of a fast and large-scale disinfection method has arisen for prevention of contagion. COUNTERFOG® is an innovative technology developed for large-scale decontamination of air and surfaces. The objective of this study is to assess experimentally the effectiveness of COUNTERFOG® in disinfecting viral-contaminated surfaces. We also aim to measure the necessary time to disinfect said surfaces. Stainless steel surfaces were contaminated with bacteriophage φ29 and disinfected using COUNTERFOG® SDR-F05A+, which uses a sodium hypochlorite solution at different concentrations and for different exposure times. A log reduction over 6 logs of virus titer is obtained in 1 min with 1.2% sodium hypochlorite when the application is direct; while at a radial distance of 5 cm from the point of application the disinfection reaches a reduction of 5.5 logs in 8 min. In the same way, a higher dilution of the sodium hypochlorite concentration (0.7% NaOCl) requires more exposure time (16 min) to obtain the same log reduction (> 6 logs). COUNTERFOG® creates, in a short time and at a distance of 2 m from the point of application, a thin layer of disinfectant that covers the surfaces. The selection of the concentration and exposure time is critical for the efficacy of disinfection. These tests demonstrate that a concentration between 0.7-1.2% sodium hypochlorite is enough for a fast and efficient ɸ29 phage inactivation. The fact that ɸ29 phage is more resistant to disinfection than SARS-CoV-2 sustains this disinfection procedure.

Aerosolized anthrax (Bacillus anthracis) spores are of extreme health concern and can remain airborne for hours and contaminate all kinds of surfaces, constituting reservoirs from which resuspension is easily produced. The assessment of decontamination techniques must therefore consider both air and surfaces. In the present study, several kinds of disinfecting fogs were experimentally tested against Bacillus thuringiensis spores, which served as a surrogate for Bacillus anthracis, both as aerosols released into the air and spread on porous and non-porous surfaces with different positions and orientations. This technology removed Bacillus thuringiensis spores from the air in 20 min with just a 1 min application of fog. The dynamics and characteristics of the fog, related to aerosol and surface interactions, proved to be critical for optimal performance and decontamination. An optimal configuration could provide effective disinfection even on indirectly reached surfaces. In all cases, 8% hydrogen peroxide (H2O2) provided a higher disinfection rate than 2% glutaraldehyde.

The COVID-19 pandemic highlighted the dangers of airborne pathogen transmission. SARS-CoV-2 is known to be transmitted through aerosols; however, little is known about the dynamics of these aerosols in real environments, the conditions, and the minimum viral load required for infection. Efficiently measuring and capturing pathogens present in the air would help to understand the infection process. Air samplers usually take several hours to obtain an air sample. In this work a fast (1-2 min) method for capturing bioaerosols into a liquid medium has been tested in hospital rooms with COVID-19 patients. This fast sampling allows detecting transient levels of aerosols in the air. SARS-CoV-2 RNA is detected in aerosols from several hospital rooms at different levels. Interestingly, there are sudden boosts of the SARS-CoV-2 load in the air, suggesting that SARS-CoV-2 could be released abundantly at certain moments. These results show that the distribution of SARS-CoV-2-containing aerosols is not homogeneous in the hospital room. This technology is a fast and effective tool for capturing airborne matter in a very short time, which allows for fast decision-making when any kind of hazard in the air is detected. It is also useful for a better understanding of aerosols dynamics.

COUNTERFOG® has been proposed as a rapid decontamination and disinfection technology that uses dynamic submicrometric-disinfecting fog cones. When projected onto surfaces, they create a micrometre-thick film of disinfectant minimizing the use of liquids and the impact on environment. The extremely thin film is intended to be enough to cover and kill microorganisms and simultaneously thin enough to evaporate in a few minutes-depending on the environmental conditions. In the present work, experimental tests were carried out to verify this hypothesis. These include a physical characterization of the fog in the cone, a measurement of the liquid flow projected on surfaces as well as disinfection tests with a series of microorganisms. In addition to these results, operational recommendations are derived to ensure disinfection reliability.

COUNTERFOG® is a CBRN decontamination and rapid disinfection technology based on the use of dynamic cones of nanometric fog which, when projected into the air, trap the CBRN agents carried by it. When the cones are projected with biocidal liquid onto surfaces, biological agents are eliminated rapidly, whether they are deposited on or adhered to the surface, floating in the air or easily resuspendable. The COUNTERFOG® SDR-F05A+ range of equipment has been developed for the rapid disinfection of facilities, buildings and vehicles by a team of one or two people. This work presents its physical characterization, a series of biological tests with various microorganisms, and the experience of use in a real operational environment carried out by the Spanish National Police in the context of the COVID-19 pandemic.

The existence of particles with diameter under 10 μm in air is strongly correlated with respiratory diseases. These particles are profusely produced by heating systems, traffic, and Diesel engines creating a serious problem to modern cities. Natural mechanisms removing particles from the atmosphere are too slow to deal with the huge amount of particles daily released by human activity. The objective of this work is to measure the effectiveness of a new technology called Counterfog® to eliminate airborne particles. The results show that Counterfog® is able to wash out PM10, PM5, and PM2.5 Diesel-generated airborne particles quite efficiently.

Nowadays, radioactive materials are widely used in medicine, agriculture, industry and scientific research. This implies a growing accessibility and their potential use for criminal or terrorist purposes, i.e. as Radioactive Dispersion Device (RDD) or as Radiation Emission Device (RED). In light of these new threats, currently there are no countermeasures available that can respond quickly and automatically to mitigate their possible consequences. Therefore, the need arises to design and to implement new countermeasure systems that will act in the face of a CBRNE (Chemical, Biological, Radiological, Nuclear and Explosives) incident, even in the presence of fire. This is the main goal of the COUNTERFOG project, which proposed a countermeasure system based on the generation of a fog that interact with the dispersed aerosols. The objectives of the project range from the design and manufacture of nozzles able to generate the required fog, to planning and execution of the experimental procedure to evaluate its effectiveness. This work presents the results of the application of the COUNTERFOG system to the cleaning of RN surrogates, dispersed in the environment simulating the detonation of a RDD device.

The Counterfog system for protection and decontamination, based on the use of fog jets, has demonstrated its usefulness across a broad spectrum of CBRN agents, including the smoke produced in fires. Its ability to trap particles, spores, microorganisms and other elements dispersed in the air, as well as to disperse nanostructured microparticles and disinfectants, means that Counterfog can be used to prevent the airborne spread of CBRN agents as well as for the decontamination of premises and facilities. This work presents results with various large-scale agent surrogates as well as with real chemical agents in the laboratory. This work has been funded by the European Commission under its FP7-SEC-2012-1 programme, grant number 312804.

The deadly properties of most of CBRN warfare agents are based on their dispersed condition. Particularly the efficiency of BRN agents needs a high surface-volume rate that is not provided by a collapsed or bulk form. The knowledge of the dynamics of fogs, smoke and dispersed materials in air should therefore be of the maximum priority. As a part of the FP7 funded project COUNTERFOG, a laboratory for experimental tests of fog dynamics has been designed and built. The results show how a fog in air can be washed out using another fog with a minimum use of water solution providing the basis for a general rapid general response system for collapsing all kinds of dispersed agents (smoke, fog, spores, etc.). The effects of temperature, humidity and other conditions is also shown. This work has been funded by FP7-SEC-2012-1 program of the EU Commission under grant number 312804.

This work presents a selective overview of natural fogs in terms of fog types, forms and states of occurrence, physical, micro-physical, chemical and dynamic properties, basic characterizing parameters, etc. In focus are related achievements and contributions reported mainly during the last decade and a half, as a result of both laboratory studies and field observations. Processes of homogeneous and heterogeneous nucleation are analyzed in the aspects of condensation, nuclei diversity and specifics, as related to the activation, growth and deposition of fog droplets. The effect is highlighted of the water vapor's partial pressure on the surface tension of the liquid water-air interface and the freezing point of the water droplets. Some problems and aspects of fog modeling, parameterization, and forecasting are outlined and discussed on the examples of newly developed relevant 1D/3D theoretical models. Important issues of fog impacts on the air quality, ecosystems, water basins, societal life, and human health are also addressed and discussed, particularly in cases of anthropogenically modified (chemical, radioactive, etc.) fogs. In view of reducing the possible negative effects of fogs, conclusions are drawn concerning the new demands and challenges to fog characterization imposed by the changing natural and social environment and the needs for new data on and approaches to more adequate observations of fog-related events.

Device for large scale fog decontamination. (White Book of the FP7 Counterfog project, no. 312804.)