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Quantification of pollutant re-introduction through ventilation openings into a building: A benchmark based on wind-tunnel experiments

Romain Guichard et al. — Mon, 19 Jan 2026 04:25:06 -0800

In occupational risk prevention, collective protection measures based on ventilation to reduce exposure to chemical hazards generally consist of containing a pollutant at its source, capturing it, and releasing it outdoors, after purification when it is applicable. However, unfiltered pollutants that are released can be re-introduced through ventilation air intakes or windows of the same building or neighbouring buildings, depending on wind conditions. Predicting the amount of pollutant re-introduced remains very challenging while essential to implement appropriate risk control measures. In this context, an experimental benchmark has been designed to quantify the dispersion and re-introduction of a pollutant in a reduced-scale building model. It accounts for the wind flow around the building, the building mechanical ventilation system, the emission and tracking of a tracer gas in an atmospheric boundary layer wind tunnel (ABLWT). In addition to measurements of tracer gas concentration in the ventilation exhaust duct for 13 wind directions (0, 15, 30, 45, 50, 60, 75, 90, 135, 180, 225, 270 and 315°) and 3 wind speeds (6.4, 9.0 and 11.1 m/s at the building model height), a mapping of the concentration inside and outside the building at the ventilation air intakes is provided for the worst-case scenario of wind conditions. This experimental data is crucial for validating, under controlled conditions, pollutant dispersion models for both outdoor and indoor environments in a computational fluid dynamics (CFD) framework, as well as for assessing ventilation network simulations using zonal or nodal approaches.

Comprehensive comparison of sampling methods for evaluating hexamethylene diisocyanate (HDI) in the air of an automotive collision repair facility

Hugues Ahientio et al. — Mon, 12 Jan 2026 07:36:53 -0800

Performance of different classes of filtering facepiece respirators toward nanoparticles

Clothilde Brochot et al. — Mon, 12 Jan 2026 07:16:03 -0800

Introduction: In the case of exposure to harmful substances and the use of a filtering facepiece respirator (FFR) to protect workers, it is important to know the performance of commercial FFR. In previous studies, the authors investigated a series of parameters on the effectiveness of a standard N95 FFR: particle diameter, airflow rate intensity, breathing simulation, time of use, relative humidity. It remains uncertain whether previous results can be extrapolated to all commercial FFRs.

Objective: To determine whether previous conclusions apply to other FFRs, an expanded selection of models was evaluated in this study. The initial penetrations are then measured in order to compare the penetrations amongst the different FFRs.

Methods: To do so, an experimental setup generates NaCl nanoparticles before introducing them into a test chamber containing the FFR. A constant flow of 85 L/min is drawn through the FFR and particle concentration is measured upstream and downstream of the FFR with a Scanning Mobility Particle Sizer. This setup allows penetration to be measured as a function of the particle diameter from 10 to 200 nm. Pressure drop was also measured across the FFR.

Results: The benchmark established in this study confirms that penetration measurements align with previously reported values. All tested FFRs exhibit comparable trends: the most penetrating particle size (MPPS) remains between 30 and 50 nanometers, with penetration decreasing for particles smaller or larger than this range.

Conclusion: The results obtained thus indicate that the outcome achieved previously for the standard N95 FFRs can be extrapolated to the other FFRs presented here.

Effect of ventilation and wearing a facemask in reducing indoor aerosol transmission

Clothilde Brochot et al. — Mon, 12 Jan 2026 06:52:56 -0800

The COVID-19 pandemic has significantly disrupted research in respiratory protection and transmission routes. Indeed, the pandemic has highlighted a number of issues, including those related to the performance and use of respiratory protective equipment such as masks and ventilation. A plethora of commercial and homemade masks have widely appeared during the pandemic, although they are not yet fully regulated in performance and fit test. However, with regard to the source reduction process, testing facemasks not at the inhalation, but at the source (exhalation) offers a new perspective on how to prevent particle emissions. Different means of transmission reduction are measured and analysed here, and different conditions were compared: the ventilation environment, the type, filtration properties and fit (leaks) of three different facemasks. It was found that ventilation greatly helped reduce the wearer's emissions at source. Additionally, while some materials are certainly more effective than others at inhibiting particle penetration, an even more important factor is the amount of leakage emitted from a mask.

Protecteurs fixes et distance de sécurité : comment aider les utilisatrices et utilisateurs à rendre l'installation sécuritaire?

Laurent Giraud — Thu, 08 Jan 2026 07:00:13 -0800

Cette conférence présente le guide conjoint produit par l’IRSST et la CNESST sur les protecteurs fixes et les distances de sécurité, dans une optique de prévention des risques mécaniques. Laurent Giraud, ex-chercheur en sécurité des machines, explique les origines de ce guide et les différentes versions qui ont été publiées depuis 2008. Il parle des choix éditoriaux et détaille les différentes parties du guide en faisant aussi un lien avec le sécurimètre. Cette conférence offre un regard éclairant sur un des moyens de réduction des risques mécaniques fortement utilisé dans toutes les entreprises, grandes et petites. Elle permet de comprendre que la mise en œuvre d'un protecteur fixe nécessite un peu de doigté et quelques réflexions afin d'obtenir un résultat sécuritaire.

Analysis of the functional and acoustical comfort of earplugs experienced by a group of workers in Canadian companies and identification of the influencing variables

Bastien Poissenot-Arrigoni et al. — Mon, 29 Dec 2025 07:05:01 -0800

Earplugs are essential for hearing protection in noisy workplaces, but their effectiveness depends heavily on user comfort, which influences proper and consistent use. This study explores functional and acoustical comfort experienced by 173 workers across Canadian companies, each testing different ’disposable or reusable’ earplug models over seven weeks. Comfort is assessed using detailed questionnaires covering six subdimensions: ease of insertion and removal, noise protection, impact on work, and discomfort related to internal and external noise perception. Linear mixed-effects models are applied within a triad framework encompassing person-, earplug-, and environment-related characteristics in order to identify those with a significant influence on functional and acoustical comfort. Results show that person-related variables are the most influential. Handedness, hearing loss, and prior HPD experience significantly impact comfort, with left-handed participants reporting greater insertion and removal discomfort—possibly due to earcanal asymmetry and dexterity differences. Several earcanal morphological features also play a role, including isoperimetric ratios, circumference at multiple cross-sections, conicity, and length. Only a few earplug-specific characteristics influence comfort outcomes. Foam expansion time is linked to reduced acoustical discomfort associated with the perception of internal sounds, while stem presence improves insertion ease. Environmental factors do not have significant effects. In the longer term, these findings call for a rethinking of the design and selection of ’disposable or reusable’ earplugs, primarily based on earcanal morphology and users’ past experience. The study also underscores the need for improved objective metrics to assess comfort and supports the development of more personalized hearing protection solutions.

Leviers pour des pratiques favorables au retour et maintien durable au travail dans les PME

Iuliana Nastasia et al. — Wed, 17 Dec 2025 06:47:00 -0800

Lors de cet événement, les scientifiques présenteront la mise en œuvre des pratiques de gestion des invalidités dans les petites et moyennes entreprises (PME), ainsi que les principaux leviers pour un retour et maintien durable au travail (RMDT). Cette conférence s’adresse à un public large de travailleuses, travailleurs et de professionnelles, professionnels de la réadaptation et de la santé et de la sécurité au travail. La conférencière et le conférencier discuteront des enjeux uniques de la gestion des incapacités dans les PME et du potentiel de la mise en place des mécanismes collaboratifs pour mieux soutenir ces entreprises dans leurs efforts à prévenir l’incapacité.

Sécurité des machines : guide : protecteurs fixes et distances de sécurité : prévention des risques mécaniques

Laurent Giraud — Thu, 11 Dec 2025 11:26:23 -0800

Laryngeal hypersensitivity from the perspective of pain science: An integrative review of empirical studies on associated factors and processes

William Saint-Jules et al. — Fri, 05 Dec 2025 12:15:54 -0800

Objective

Laryngeal hypersensitivity (LHS) is a state of heightened sensorimotor response to stimuli in the upper airway. Although its clinical picture is becoming progressively clearer with recent research progress, specificities about its associated factors and processes remain to be clarified. The aim of this integrative review was to synthesize published empirical data from human studies on LHS, focusing on related factors and pathophysiology.

Study Design and Data Sources

Integrative review of the literature; Pubmed, EMBASE, and Web of Science.

Methods

Keywords associated with the following three main concepts were used to query databases: (1) manifestations potentially associated with an irritable larynx (dysphonia, inducible laryngeal obstruction (ILO), chronic cough, and globus); (2) hypersensitivity; and (3) pathophysiology. Peer-reviewed studies in English providing empirical original research data on the pathophysiology of LHS were included, with no restriction based on study design.

Results

In total, 54 papers met the inclusion criteria. Factors potentially associated with LHS were identified, namely (1) psychological and lifestyle factors, (2) upper airway inflammation and injuries from exogenous/endogenous irritants, infections, or mucosal atrophy, (3) sex hormones, (4) metabolic abnormalities, and (5) aberrant respiratory behavior. Given the parallels between pain-related mechanisms and suggested LHS mechanisms, processes identified as putatively contributing to LHS were categorized in light of the current pain literature. Findings suggest that LHS may stem from a peripheral tissue insult, a neuropathic insult, and/or maladaptive neuroplasticity. Gaps in the literature were identified, in part driven by an uneven repartition of research across the various alleged manifestations of LHS. In fact, a large majority of studies pertained to chronic cough, with very few addressing muscle tension dysphonia, ILO, and globus.

Conclusion

Future research can focus on the potential role of hypersensitivity in manifestations such as muscle tension dysphonia and ILO, and on the development of guidelines to identify the specific underlying factors and mechanisms at play in LHS symptoms.

Arm differences in muscle activity characteristics during a bilateral simulated overhead work in right-handed and ambidextrous individuals

Erika Renda et al. — Fri, 05 Dec 2025 12:08:13 -0800

Background:

Many work tasks use both arms to execute in-phase bilateral movements above shoulders. However, bilateral limb asymmetries have been proposed to be a possible cause for injuries. Additionally, the dominant arm is more predisposed to musculoskeletal injuries. Should we assume that both arms’ exposure to injury risk factors is the same during a bilateral task, and is not impacted by handedness and sex? Purpose: We measured the effects of sex and fatigue on activity of bilateral shoulder muscle activity during a bilateral fatiguing overhead shoulder flexion task, among right-handed or ambidextrous individuals. Methods: Twenty-five healthy adults (13 males) completed a bilateral overhead fatiguing task with repetitive shoulder flexions from 90° to 135°. Exposure was measured using electromyographic data from six bilateral shoulder muscles, and their activation amplitude (RMS) and movement-to-movement variability (SD) were quantified. Data were analyzed separately for right-handed (n = 18) and ambidextrous (n = 6) males and females. One male participant was left-handed. Results: With fatigue, right-handed females had greater anterior deltoid activation in the dominant arm, whereas ambidextrous females showed increased activation of their right infraspinatus. All females had greater middle deltoid activation variability in the left arm compared to the right. In contrast, right-handed males had more middle deltoid activation amplitude and variability in their left arm, but otherwise had fewer arm differences. Conclusion: Our results indicate more impact of a bilateral fatiguing task on arm electromyographic asymmetries among females. Thus, job rotation such as alternating arms may pose a greater injury risk for females, since their shoulders show a clearer side dominance. Thus, to enhance human health and safety in a workplace, handedness and sex should be considered, and muscle activity measured, when implementing job/task rotation for exposure variation at work.

Vocational training and occupational health: An ergonomics approach to gender and disabilities for social sustainability

Myriam Bérubé et al. — Fri, 05 Dec 2025 12:08:07 -0800

The Work-Oriented Training Path (WOTP) in Quebec, Canada, is a dual vocational training program that offers students with learning difficulties supervised traineeships. Teachers play a pivotal role in managing students' occupational health and safety (OHS), yet must do so under tight time constraints, limited institutional guidance and highly diverse student profiles. Building on an activity-centered ergonomics and capabilities framework, this multiple-case study explores how gender, disabilities, and work determinants shape OHS management within the WOTP, emphasizing their implications for social sustainability. Twenty-seven semi-structured interviews were conducted with 15 WOTP teachers; 497 narrated anecdotes, which are units of speech when teachers' talk about students, were thematically analyzed to capture everyday mechanisms that expand or restrict safe participation in traineeship. The findings highlight challenges stemming from power dynamics between teachers, parents, and employers, which influence the operational leeway available for teachers to implement OHS prevention. Their work organization, conditions and tools also expand or restrict their capability to have an equitable approach. Additionally, the analysis reveals disparities in traineeship placement opportunities and OHS prevention, particularly concerning students’ gender identity and disabilities. Key factors influencing traineeship placements and OHS practices included students' communication skills, perceived autonomy, and suitability of behavior compared to social norms. Students with disabilities are frequently assigned repetitive tasks, increasing exposure to hazards that remain under-recognized. These results underscore the critical need for inclusive OHS prevention, fostering a more socially sustainable approach within vocational training programs.

Détermination de la concentration des métaux de la faction inhalable dans l'air par ICP-MS avec prélèvement effectué sur DIS

Sébastien Gagné et al. — Fri, 05 Dec 2025 07:45:27 -0800

Détermination de la concentration des métaux des fractions inhalable et respirable dans l'air par ICP-MS avec prélèvement effectué sur DRS

Sébastien Gagné et al. — Fri, 05 Dec 2025 07:45:23 -0800

Prélèvement de surface sur écouvillon

Delphine Lanoie — Tue, 02 Dec 2025 05:36:56 -0800

Cette vidéo montre comment effectuer un prélèvement de surface avec un écouvillon pour l’analyse de bactéries et de moisissures cultivables.

Documents associés :

I-MAT-048

MA-340 Identification des moisissures cultivables

MA-341 Indentification des bactéries cultivables

Identifying high-risk workplaces for radon: The role of buildings’ foundations and underground water sources

Sabrina Gravel et al. — Wed, 26 Nov 2025 12:40:23 -0800

OBJECTIVE: Radon, a naturally occurring lung carcinogen, can seep into buildings and expose occupants, including workers. Our aim is to describe radon exposure in various workplaces, identify factors associated with exposure, and highlight levers for preventive action.

MATERIAL AND METHODS: Workplaces with an underground or slab-on-grade work area were recruited in four regions of Quebec (Central Canada) with high and low potential for radon emissions. Long-term radon samples were taken during the cold season with Alpha Track AT-100 passive dosimeters, deployed by the research team in accordance with Health Canada's Guide for radon measurements in public buildings.

RESULTS: There were 354 radon measurements in 57 buildings constructed between 1877 and 2021 (54 workplaces), with on average six measurements (1-28) per workplace during a median of 109 days. Ten buildings had all measurements below the detection limit (15 Bq/m(3)), and six had at least one measurement above 100 Bq/m(3). The highest values recorded were in a fish hatchery (>1500 Bq/m(3)). Generalized estimating equations revealed that a lowest floor made of materials other than poured concrete, the presence of naturally occurring radioactive material (underground water), and a small building footprint were the most predictive factors of higher concentrations, regardless of the regional radon emission potential.

CONCLUSION: In this convenience sample, most workplaces presented radon concentrations well below guidelines. However, the surprise expressed by workplace managers and public health officials regarding high concentrations associated with NORM is evidence of a lack of awareness of the dangers of radon in these environments. (©Elsevier)

Grille des observations et des caractéristiques des ateliers de carrosserie

Jules Turcot et al. — Mon, 17 Nov 2025 11:49:18 -0800

Experimental atmosphere monitoring in gasoline vapor inhalation studies

Prem Kumarathasan et al. — Mon, 17 Nov 2025 11:44:03 -0800

Conditions affecting the composition and stability of test atmospheres of gasoline were investigated. Vapor was generated at 60°C from a methanol-gasoline blend (85:15, v:v) in a carrier air flow (25 L/min) and mixed with dilution air (580 L/min) for distribution to 2.5-m³ inhalation chambers. Three nominal concentrations (equivalent to 5150, 515, 51.5 ppm methanol) were produced under dynamic flow conditions. Analyses of vapor were carried out by gas chromatography with mass spectrometer and flame ionization detectors. Analyte concentrations determined for the high, medium, and low exposure levels were within ±1%, ±4%, and ±7% of the nominal values, respectively. Within-day variation and day-to-day variation in the analyte concentrations were < 5%. Virtually constant levels of low boiling (< 115°C) components (e.g., 2,2,4-trimethyl pentane) were observed over a daily 6-h exposure period. However, increase in high boilers such as 1,3,5-trimethyl benzene in the vapor with time was associated with the accumulation of residue in the vapor generation system. Variations in composition between three distinct batches of gasoline were also documented. Physiologically based pharmacokinetic modeling predicted a sensitivity of internal doses of benzene, toluene, and xylene in rats to the batch-to-batch variability in composition of gasoline due to kinetic interactions. The data illustrate some complexities of the assessment of chemical mixtures of environmental relevance. Adequate analytical and dose modeling methods should be applied to the characterization of experimental conditions in view of the heterogeneous nature of gasoline.

Reduced atmospheric manganese in Montreal following removal of methylcyclopentadienyl manganese tricarbonyl (MMT)

Alexandre Joly et al. — Mon, 17 Nov 2025 11:43:56 -0800

Methylcyclopentadienyl manganese tricarbonyl (MMT) was used between 1990 and 2003 as an antiknock agent and as an octane booster in Canadian unleaded gasoline. Its combustion leads to Mn emissions. The objective of this research was to examine the variations in atmospheric Mn in Montreal (Canada) from 2001 to 2007, covering the period prior (2001–2003) to and following (2005–2007) MMT use. Three sampling stations were selected because of their proximity to roads with widely differing and well-known traffic patterns. Filters from 2001 to 2007 were obtained from the Montreal Urban Community. The first sample of each month was selected, and Mn analysis was performed by neutron activation analysis. Total suspended particulates (TSP) was calculated by weighing the filters before and after dust collection. Results show a significant decrease of Mn over time at each station, whereas TSP decreased significantly in two stations. Comparing atmospheric Mn during and after the period of use of MMT 2001–2003 vs 2005–2007 showed a significant decrease at all stations. For TSP, only one station showed borderline significant decline between these two periods. Overall, between the two periods, Mn and TSP decreased by 39% and 17%, respectively. These data suggest that the combustion of MMT led to an increase of airborne Mn of approximately 22%. These findings should help in decision-making processes concerning the use of MMT in gasoline in other countries.

Condensation sampler efficiency for the recovery and infectivity preservation of viral bioaerosols

Jodelle Degois et al. — Mon, 17 Nov 2025 07:52:21 -0800

Une meilleure compréhension des voies de transmission aéroportée des virus responsables d’infections nosocomiales nécessite des méthodes d’échantillonnage efficaces et précises, capables de préserver l’intégrité et l’infectiosité virales. Ce projet visait à comparer l’efficacité de collecte des virus entre l’échantillonnage traditionnel par filtre et cassette, et l’échantillonnage par condensation en flux laminaire. Des bactériophages (MS2, PhiX174, Phi6 et PR772) ainsi qu’un virus influenza ont été nébulisés dans une chambre d’aérosols. Les bioaérosols ont été simultanément prélevés sur des filtres en polycarbonate (0,8 µm) placés dans des cassettes fermées de 37 mm (CFC) et à l’aide d’un échantillonneur à condensation (Spot Sampler™), qui recueille les particules dans une solution liquide. Les concentrations virales ont été évaluées après 60 minutes et 4 heures d’échantillonnage, à la fois par culture (préservation de l’infectiosité) et par qPCR (rendement de récupération), afin de comparer les performances des deux dispositifs. Le phage PhiX174 a montré une meilleure récupération avec le Spot Sampler™ à tous les temps, tandis que PR772 présentait une meilleure récupération génomique relative avec le CFC après 60 minutes. De plus, le Spot Sampler™ a permis une meilleure conservation de l’infectiosité pour l’ensemble des virus testés, y compris l’influenza, à l’exception du phage MS2 après 4 heures. Ces résultats suggèrent que le Spot Sampler™ constitue une méthode prometteuse pour l’étude de la transmission aéroportée des virus en milieu hospitalier, ou pour évaluer en laboratoire l’efficacité de dispositifs de traitement de l’air virucides.

Ozone efficacy for the control of airborne viruses: Bacteriophage and norovirus models

Marie-Eve Dubuis et al. — Mon, 17 Nov 2025 07:52:12 -0800

Cette étude visait à évaluer l’efficacité d’un traitement de l’air combinant l’ozone et l’humidité relative (HR) pour l’inactivation des virus aéroportés. Quatre bactériophages (φX174, PR772, MS2 et φ6) ainsi qu’un virus eucaryote (norovirus murin MNV-1) ont été exposés à de faibles concentrations d’ozone (1,23 ppm pour les phages et 0,23 ppm pour le MNV-1) et à différents niveaux d’humidité relative pendant des durées variant de 10 à 70 minutes. L’inactivation virale a ensuite été mesurée afin d’identifier les conditions les plus efficaces pour réduire l’infectiosité. Une diminution d’au moins deux ordres de grandeur de l’infectiosité a été observée pour φX174, MS2 et MNV-1 après une exposition de 40 minutes à 85 % d’humidité relative. Pour PR772 et φ6, une exposition de 10 minutes à la condition de référence (20 % HR) a produit des effets similaires. Ces résultats démontrent que l’ozone, utilisé à faible concentration, constitue un désinfectant puissant contre les virus aéroportés, surtout lorsqu’il est combiné à un taux d’humidité élevé. Cette approche pourrait être envisagée comme méthode de traitement de l’air dans les environnements hospitaliers à ventilation naturelle, afin de limiter la transmission des agents viraux dans l’air et d’améliorer la biosécurité dans les milieux de soins.

Abstract

This study was designed to test the efficacy of an air treatment using ozone and relative humidity (RH) for the inactivation of airborne viruses. Four phages (φX174, PR772, MS2 and φ6) and one eukaryotic virus (murine norovirus MNV-1) were exposed to low ozone concentrations (1.23 ppm for phages and 0.23 ppm for MNV-1) and various levels of RH for 10 to 70 minutes. The inactivation of these viruses was then assessed to determine which of the tested conditions provided the greatest reduction in virus infectivity. An inactivation of at least two orders of magnitude for φX174, MS2 and MNV-1 was achieved with an ozone exposure of 40 minutes at 85% RH. For PR772 and φ6, exposure to the reference condition at 20% RH for 10 minutes yielded the same results. These findings suggest that ozone used at a low concentration is a powerful disinfectant for airborne viruses when combined with a high RH. Air treatment could therefore be implemented inside hospital rooms ventilated naturally.