Manikin Face Research Articles

Performance evaluation of surgical, N95 and FFP2 respiratory masks by manikin-based sampling system for assessing the protection against airborne dust

In this study, the particle penetration through various respirator filters (N95, FFP2 and surgical) were measured by manikin-based sampling system. In the months of June to November, 102 samples were taken for 44 days. A specific flow (9 L per minute) of air containing suspended particles (about 1.05 m3) was passed through the breathing filters and the particle leakage was determined. The personal cascade impactor (Sioutas, SKC) was utilized in order to classification of penetrated particles in the ranges of 2.5, 1 and 0.5 μm. Protective performance of masks installed on the manikin face is increased from the surgical to the N95 and the FFP2 mask. There was no significant difference between the performance of N95 and FFP2 but there is a significant difference between performances of these two masks with surgical mask. Due to the non-flexibility of the N95 and its lack of fixation on the face, the amount of penetration is higher than FFP2. Despite of lower price (FFP2 0.4 $, surgical 0.1 $, N95 0.6 $) and structural feature (double layer structure), FFP2 has the highest performance amongst the three types of masks studied. The results suggest the use of FFP2 masks to protect against dust contamination.

Evaluation of a Filtering Facepiece Respirator and a Pleated Particulate Respirator in Filtering Ultrafine Particles and Submicron Particles in Welding and Asphalt Plant Work Environments.

Manufacturing sites, such as welding, casting, and asphalt production (fumes), generate vast numbers of ultrafine particles of <0.1 µm in size and submicron particles close to the ultrafine range (0.1–0.5 µm). Although cumulative masses of these particles are negligible in comparison to the larger particles, the health effects are more severe due to the higher penetration in the human lower respiratory tract, other body parts crossing the respiratory epithelial layers, and the larger surface area. This research investigates the effectiveness of two common commercially available N95 filtering facepieces and N95 pleated particulate respirator models against ultrafine and submicron particles. Two specific types of respirators, the N95 filtering facepiece and the N95 pleated particulate models, in both sealed and unsealed conditions to the manikin face, were tested at various commercial and academic manufacturing sites, a welding and foundry site, and an asphalt production plant. Two TSI Nanoscan SMPS nanoparticle counters were used simultaneously to collect data for particles of 10–420 nm in size from inside and outside of the respirators. While one of them represented the workplace exposure levels, the other one accounted for the exposure upon filtration through the respiratory surfaces. The results showed the particles generated by these manufacturing operations were mostly within the range of from 40 to 200 nm. Results also indicated that while the percentage of filtration levels varied based on the particle size, it remained mostly within the desired protection level of 95% for both of the N95 respirator models in sealed conditions and even for the N95 pleated particulate model in the unsealed condition. However, in the case of the N95 filtering facepiece model, unsealed respirators showed that the percentage of penetration was very high, decreasing the protection levels to 60% in some cases. Although the number of workplace airborne particle levels varied considerably, the filtration percentages were relatively consistent.

Investigation of the protection efficacy of face shields against aerosol cough droplets

Simple plastic face shields have numerous practical advantages over regular surgical masks. In light of the spreading COVID-19 pandemic, the potential of face shields as a substitution for surgical masks was investigated. In order to determine the efficacy of the protective equipment we used a cough simulator. The protective equipment considered was placed on a manikin head that simulated human breathing. Concentration and size distribution of small particles that reached the manikin respiration pathways during the few tens of seconds following the cough event were monitored. Additionally, water sensitive papers were taped on the tested protective equipment and the manikin face. In the case of frontal exposure, for droplet diameter larger than 3 μm, the shield efficiency in blocking cough droplets was found to be comparable to that of regular surgical masks, with enhanced protection for portions of the face that the mask does not cover. Additionally, for finer particles, down to 0.3 µm diameter, a shield blocked about 10 times more fine particles than the surgical mask. When exposure from the side was considered, the performance of the shield was found to depend dramatically on its geometry. While a narrow shield allowed more droplets and aerosol to penetrate in comparison to a mask under the same configuration, a slightly wider shield significantly improved the performance. The source control potential of shields was also investigated. A shield, and alternatively, a surgical mask, were placed on the cough simulator, while the breathing simulator, situated 60 cm away in the jet direction, remained totally exposed. In both cases, no droplets or particles were found in the vicinity of the breathing simulator. Conducted experiments were limited to short time periods after expiratory events, and do not include longer time ranges associated with exposure to suspended aerosol. Thus, additional evidence regarding the risk posed by floating aerosol is needed to establish practical conclusions regarding actual transmittance reduction potential of face shields and surgical face masks.

Numerical investigation of airborne contaminant transport under different vortex structures in the aircraft cabin

Airborne contaminants such as pathogens, odors and CO2 released from an individual passenger could spread via air flow in an aircraft cabin and make other passengers unhealthy and uncomfortable. In this study, we introduced the airflow vortex structure to analyze how airflow patterns affected contaminant transport in an aircraft cabin. Experimental data regarding airflow patterns were used to validate a computational fluid dynamics (CFD) model. Using the validated CFD model, we investigated the effects of the airflow vortex structure on contaminant transmission based on quantitative analysis. It was found that the contaminant source located in a vorticity-dominated region was more likely to be “locked” in the vortex, resulting in higher 62% higher average concentration and 14% longer residual time than that when the source was on a deformation dominated location. The contaminant concentrations also differed between the front and rear parts of the cabin because of different airflow structures. Contaminant released close to the heated manikin face was likely to be transported backward according to its distribution mean position. Based on these results, the air flow patterns inside aircraft cabins can potentially be improved to better control the spread of airborne contaminant.

The distribution of biologically effective UV spectral irradiances received on a manikin face that cause erythema and skin cancer

Solar ultraviolet (UV) radiation is a major cause of erythema and skin cancer in humans and the face is one of the highest risk sites. Biologically effective UV irradiation (UVBE) is wavelength-dependent, and risk assessment has been demonstrated based on the value of the received UV radiation. Therefore, this study measured the face skin exposure to UV spectral irradiance using a spectroradiometer and a head manikin, which were weighted by action spectra to calculate the UVBE that causes erythema (UVBEery), non-melanoma (UVBEnon-mel), human squamous cell cancer (UVBEh-SCC), and DNA damage (UVBEDNA-d). We determined that the biologically effective UVB and UVA irradiances on clear sky days had peak values at 65–73° SEA (8–9 UVI) and 55–68° SEA (6–7 UVI), respectively. In the 10–30° SEA range, the highly skin-damaging wavelengths were all observed at 300nm. However, in the 30–60°, 60–81°, and 10–81° SEA ranges, the highly skin damaging wavelengths were 300nm, 304nm and 300nm for UVBEery, respectively; 304nm, 306nm and 304nm for UVBEnon-mel, respectively; all 305nm for UVBEh-SCC, and two small peaks at 302nm and 312nm for UVBEDNA-d.

Experimental study of the effects of human movement on the convective heat transfer coefficient

This present study is dedicated to the analysis of the effects of moving speed, moving direction angle and temperature difference between human body and environment on the convective heat transfer coefficients of the human body. The experiments were carried out in a full-scale cabin with a thermal manikin. Five moving speeds of the manikin (0.2, 0.5, 0.8, 1.1 and 1.3m/s) were carried out with a motor on a 10m-length-rail, and four temperature differences were selected (4, 8, 12 and 16°C) by changing the heating power of the manikin. Eight moving direction angles between the moving direction and the manikin face were set. In each experimental case, the temperatures of the environment and the wall in different heights were measured by the thermocouples to calculate the convective heat transfer coefficients. Through comparison with experimental data of the human body in wind tunnel, it can be demonstrated that the effect of the moving speed on the convective heat transfer coefficients is weaker than that of wind speed for the trunk parts of the manikin, while stronger for the upper limbs. The convective heat transfer coefficients are obviously affected by the moving direction angles under the moving condition for different body parts: in general the body parts having higher convective heat losses when they move against the wind. The experimental results also show that the convective heat transfer coefficients increase as the moving speeds and the temperature differences, i.e., the higher values correspond to the higher speeds and the higher temperature differences.

Advanced air distribution for minimizing airborne cross-infection in aircraft cabins

The performance of personalized ventilation combined with local exhaust at each seat was studied for the purpose of minimizing airborne cross-infection in spaces whose occupants are sedentary, such as transportation environments. Experiments were carried out in a simulated aircraft cabin section (3 rows, 21 seats). One breathing thermal manikin simulated an “infected” passenger as a source of pollution, and a second breathing manikin simulated an “exposed” passenger. The personalized ventilation supplied clean air at 6 or 10 L/s (12.7 of 21.2 cfm) from in front of each manikin's face. Air was withdrawn at a rate of 6 or 10 L/s (12.7 or (21.2 cfm) by the local exhaust system, which consisted of two exhaust terminals, one on each side of the head of the “infected” manikin. The cabin was ventilated with 180 L/s (381 cfm) of fresh air. Freon was mixed with the air exhaled by the “infected” manikin to simulate airborne pathogens. The airflow from the personalized supply outlet pushed the contaminated exhaled air backward, where it was exhausted before it had mixed with cabin air. This resulted in a substantial decrease of the tracer gas concentration in the air inhaled by the “exposed” manikin and in the air exhausted from the cabin.

Large Particle Penetration through N95 Respirator Filters and Facepiece Leaks with Cyclic Flow

The aim of this study was to investigate respirator filter and faceseal penetration of particles representing bacterial and fungal spore size ranges (0.7-4 mum). First, field experiments were conducted to determine workplace protection factors (WPFs) for a typical N95 filtering facepiece respirator (FFR). These data (average WPF = 515) were then used to position the FFR on a manikin to simulate realistic donning conditions for laboratory experiments. Filter penetration was also measured after the FFR was fully sealed on the manikin face. This value was deducted from the total penetration (obtained from tests with the partially sealed FFR) to determine the faceseal penetration. All manikin experiments were repeated using three sinusoidal breathing flow patterns corresponding to mean inspiratory flow rates of 15, 30, and 85 l min(-1). The faceseal penetration varied from 0.1 to 1.1% and decreased with increasing particle size (P < 0.001) and breathing rate (P < 0.001). The fractions of aerosols penetrating through the faceseal leakage varied from 0.66 to 0.94. In conclusion, even for a well-fitting FFR respirator, most particle penetration occurs through faceseal leakage, which varies with breathing flow rate and particle size.

Decreasing peak flow rate with a new bag-valve-mask device: effects on respiratory mechanics, and gas distribution in a bench model of an unprotected airway

Reducing inspiratory flow rate and peak airway pressure may be important in order to minimise the risk of stomach inflation when ventilating an unprotected airway with positive pressure ventilation. The purpose of this study was to assess the effects of a newly developed bag-valve-mask device (SMART BAG ®, O-Two Systems International, Ont., Canada) that limits peak inspiratory flow. A bench model simulating a patient with an unintubated airway was used consisting of a face mask, manikin head, training lung (lung compliance, 100 ml/cm H 2O, airway resistance 4 cm H 2O/l/s, lower oesophageal sphincter pressure 20 cm H 2O and simulated stomach). Twenty nurses were randomised to each ventilate the manikin using a standard single person technique for 1 min (respiratory rate, 12/min) with either a standard adult self-inflating bag, or the SMART BAG ®. The volunteers were blinded to the experimental design of the model until completion of the experimental protocol. The SMART BAG ® vs. standard self-inflating bag resulted in significantly ( P<0.05) lower mean±S.D. peak inspiratory flow rates (32±2 vs. 61±13 l/min), peak inspiratory pressure (12±2 vs. 17±2 cm H 2O), lung tidal volumes (525±111 vs. 680±154 ml) and stomach tidal volumes (0±0 vs. 17±36 ml), longer inspiratory times (1.9±0.3 vs. 1.5±0.3 s), but significantly higher mask leakage (26±13 vs. 14±8%); mask tidal volumes (700±104 vs. 785±172 ml) were comparable. The mask leakage observed is not an uncommon factor in bag-valve-mask ventilation with leakage fractions of 25–40% having been previously reported. The differences observed between the standard BVM and the SMART BAG ® are due more to the anatomical design of the mask and the non-anatomical shape of the manikin face than the function of the device. Future studies should remove the mask to manikin interface and should introduce a standardized mask leakage fraction. The use of a two-person technique may have removed the problem of mask leakage. In conclusion, using the SMART BAG ® during simulated ventilation of an unintubated patient in respiratory arrest significantly decreased inspiratory flow rate, peak inspiratory pressure, stomach tidal volume, and resulted in a significantly longer inspiratory time when compared to a standard self-inflating bag.

Ventilation efficiencies of desk-mounted task/ambient conditioning systems.

In laboratory experiments, we investigated two task/ambient conditioning systems with air supplied from desk-mounted air outlets to efficiently ventilate the breathing zone of heated manikins seated at desks. In most experiments, the task conditioning systems provided outside air while a conventional ventilation system provided additional space cooling but no outside air. Air change effectiveness (i.e., exhaust air age divided by age of air at the manikin's face) was measured with a tracer gas step-up procedure. Other tracer gases simulated the release of pollutants from nearby occupants and from the floor covering, and the associated pollutant removal efficiencies (i.e., exhaust air concentrations divided by concentrations at manikin's face) were calculated. High values of air change effectiveness (approximately 1.3 to 1.9) and high values of pollutant removal efficiency (approximately 1.2 to 1.6) were measured when these task conditioning systems supplied 100% outdoor air at a flow rate of 7 to 9 L s-1 per occupant. Air change effectiveness was reasonably well correlated with the pollutant removal efficiency. Overall, the experimental data suggest that these task/ambient conditioning systems can be used to improve ventilation and air quality or to save energy while maintaining a typical level of IAQ at the breathing zone.

Herpes simplex virus and CPR training manikins: Reducing the risk of cross-infection

Two disinfecting solutions for removing herpes simplex virus (HSV) from CPR training manikin face skin were investigated. Both 70% ethanol and 70% ethanol plus 0.5% chlorhexidine solutions were effective in reducing recoverable virus at both 10(5) and 10(7) particles per milliliter inoculum concentrations (P less than .01 and P less than .005 versus no decontamination, respectively). The survival characteristics of HSV on manikin skin also were explored, demonstrating greater than four hours of viability.

Common Materials for Emergency Respiratory Protection: Leakage Tests with a Manikin

In areas where respirators are not routinely used, emergencies (such as fires) may occur in which protection from airborne particles is necessary. The following readily available materials were tested on a manikin connected to a breathing simulator to determine the fraction of an approximately 2-micron diameter aerosol that would leak around the seal between the materials and the manikin's face: cotton/polyester shirt material, cotton handkerchief material, toweling (a wash cloth), a surgical mask (Johnson & Johnson Co., Model HRI 8137), and a NIOSH-approved disposable face mask (3M Corp., Model #8710). The leakage tests were done to supplement the measurements of penetration through the materials reported previously. Leakage fractions were determined by comparing the penetration of the same aerosol for the materials held to the face versus being fully taped to the face. At a breathing rate of 37 liters per minute, mean leakages for the materials ranged from 0.0 percent to 63 percent, depending on the material. Mean penetrations exclusive of leakage ranged from 0.6 percent to 39 percent. Use of nylon hosiery material ("panty hose") to hold the handkerchief material or the disposable face mask to the face was found to be very effective in preventing leakage. Such a combination could be expected to reduce leakage around the handkerchief to about 10 percent or less in practice, and around the mask to less than one percent, which suggests the adaptation and use of such an approach for industrial hygiene.

ACARD report

Airborne contaminants such as pathogens, odors and CO2 released from an individual passenger could spread via air flow in an aircraft cabin and make other passengers unhealthy and uncomfortable. In this study, we introduced the airflow vortex structure to analyze how airflow patterns affected contaminant transport in an aircraft cabin. Experimental data regarding airflow patterns were used to validate a computational fluid dynamics (CFD) model. Using the validated CFD model, we investigated the effects of the airflow vortex structure on contaminant transmission based on quantitative analysis. It was found that the contaminant source located in a vorticity-dominated region was more likely to be “locked” in the vortex, resulting in higher 62% higher average concentration and 14% longer residual time than that when the source was on a deformation dominated location. The contaminant concentrations also differed between the front and rear parts of the cabin because of different airflow structures. Contaminant released close to the heated manikin face was likely to be transported backward according to its distribution mean position. Based on these results, the air flow patterns inside aircraft cabins can potentially be improved to better control the spread of airborne contaminant.