Filtration of nanoparticles applied in general ventilation (original) (raw)
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Development of a procedure to measure the performance of ventilation filters for nanoparticles
IOP Conference Series: Materials Science and Engineering, 2019
Filtration is a simple and effective way to capture particles of different sizes used in different workplaces. However, the state of current knowledge has shown that the performance of entire filter depending on the particle size are still very limited. The main objective has therefore been to develop a procedure to evaluate the filter performance used in ventilation systems for particles smaller than 300 nm including nanoparticles. The measurement procedure has been validated by comparing the penetration measurements on two different setups for nanoparticles.
Performance of mechanical filters used in general ventilation against nanoparticles
IOP Conference Series: Materials Science and Engineering, 2019
Filtration is a simple and effective way to capture particles of different sizes. According to ANSI/ASHRAE 52.2 standard, ventilation filters efficiency is tested for particles ranging from 0.3 to 10.0 μm. To our knowledge, performances of entire filters for nanoparticles are still very limited and particle size of 300 nm is commonly used as the Most Particle Penetration Size (for mechanical media). In order to evaluate the filter performance for nanoparticles, five type of filters (from MERV 8 to HEPA) were evaluated via two measurements: penetration and pressure drop. Results are consistent with previous experimental measurements on media and entire filters. These data show that the range of 150 to 500 nm is a better estimation of the MPPS, unlike the fixed diameter of 300 nm.
Measurement, 2019
Nanoparticles (NPs) are particles of less than or equal to 100 nm in diameter. Due to their size, they have a significant effect on health and safety of people. Capture of these NPs in general ventilation systems by filters remains one of the most widely used means of protection due to its relative simplicity of implementation and its effectiveness for capturing various size of particles. In North America, filters used in general ventilation systems are tested by the ANSI/ASHRAE Standard 52.2 and are graded according to their efficiency, which is a function of particle diameter. However, the current standard limits the filtration efficiency assessment for particles between 0.3 and 10.0 mm. There is therefore a significant lack of knowledge about the behavior of these filters with respect to the particle diameter below 0.3 mm considering the overall filter used in general ventilation. The main objective of this study was to develop a measurement procedure to evaluate the effectiveness of mechanical filters used in general ventilation systems against NPs. In this regard, a small setup was designed, build and qualified. Then measurement procedure was validated by comparing the penetration measurements with those obtained on qualified big loop setup for nanoparticles, which was inspired by ASHRAE. One type of mechanical filter rated (MERV 8) in three depth sizes (2.54, 5.08 and 10.16 cm) was used to compare the penetrations. The obtained results are consistent with the classical filtration theory for mechanical media and with previous experimental measurements on media. The data presented in this study show that the penetration range of 0.7-1.0 obtained for particle range 22.1-294.3 nm and at 1.00 and 0.75 m/s gives a fairly good correlation (R2 = 0.898) between the two setups. The outcome results validate the methodology used to evaluate the effectiveness of one mechanical filter used in general ventilation systems against nanoparticles by using the small setup.
Industrial Health, 2010
There is an increasing concern about the health hazard posed to workers exposed to inhalation of nanoparticles. Inhaling nanoparticles posses an occupational hazard due to elevated amount emitted to the atmosphere and working environment. Nanoparticles have potential toxic properties: the high particle surface area, number concentration, and surface reactivity. Inhalation, the most common route of nanoparticle exposure, has been shown to cause adverse effects on pulmonary functions and the deposited particles in the lung can be translocated to the blood system by passing through the pulmonary protection barriers. Filtration is the simplest and most common method of aerosol control. It is widely used in mechanical ventilation and respiratory protection. However, concerns have been raised regarding the effectiveness of the filters for capturing nanoparticles. This paper reviews the literature on the filtration performance of mechanical filters and respirators against nanoparticles. It includes the discussion about filtration mechanisms, theoretical models, affecting factors of the filtration efficiency, and testing protocols for respirator and filter certification.
2012
There is an increasing concern about the potential health hazards posed to workers exposed to inhalation of nanoparticles (NPs). Common sources of nanoparticles in working environments include fumes and exhausts from different processes like laser ablation and milling. Nanoparticles have potential toxic properties: a high particle surface area, number concentration, and surface reactivity. Inhalation, the most common route of nanoparticle exposure, has been shown to cause adverse effects on pulmonary functions, and the deposited particles in the lung can be translocated to the blood system by passing through the pulmonary protection barriers. Filtration is the simplest and most common method of aerosol control. It is widely used in mechanical ventilation and respiratory protection. However, concerns have been raised regarding the effectiveness of filters for capturing nanoparticles.
Evaluation of filter media for particle number, surface area and mass penetrations
The Annals of occupational hygiene, 2012
The National Institute for Occupational Safety and Health (NIOSH) developed a standard for respirator certification under 42 CFR Part 84, using a TSI 8130 automated filter tester with photometers. A recent study showed that photometric detection methods may not be sensitive for measuring engineered nanoparticles. Present NIOSH standards for penetration measurement are mass-based; however, the threshold limit value/permissible exposure limit for an engineered nanoparticle worker exposure is not yet clear. There is lack of standardized filter test development for engineered nanoparticles, and development of a simple nanoparticle filter test is indicated. To better understand the filter performance against engineered nanoparticles and correlations among different tests, initial penetration levels of one fiberglass and two electret filter media were measured using a series of polydisperse and monodisperse aerosol test methods at two different laboratories (University of Minnesota Partic...
Annals of Occupational Hygiene, 2009
The National Institute for Occupational Safety and Health (NIOSH) and European Norms (ENs) employ different test protocols for evaluation of air-purifying particulate respirators commonly referred to as filtering facepiece respirators (FFR). The relative performance of the NIOSH-approved and EN-certified 'Conformité Européen' (CE)-marked FFR is not well studied. NIOSH requires a minimum of 95 and 99.97% efficiencies for N95 and P100 FFR, respectively; meanwhile, the EN requires 94 and 99% efficiencies for FFRs, class P2 (FFP2) and class P3 (FFP3), respectively. To better understand the filtration performance of NIOSH-and CE-marked FFRs, initial penetration levels of N95, P100, FFP2 and FFP3 respirators were measured using a series of polydisperse and monodisperse aerosol test methods and compared. Initial penetration levels of polydisperse NaCl aerosols [mass median diameter (MMD) of 238 nm] were measured using a method similar to the NIOSH respirator certification test method. Monodisperse aerosol penetrations were measured using silver particles for 4-30 nm and NaCl particles for 20-400 nm ranges. Two models for each FFR type were selected and five samples from each model were tested against charge neutralized aerosol particles at 85 l min 21 flow rate. Penetrations from the 238 nm MMD polydisperse aerosol test were <1% for N95 and FFP2 models and <0.03% for P100 and FFP3 models. Monodisperse aerosol penetration levels showed that the most penetrating particle size (MPPS) was in the 30-60 nm range for all models of FFRs tested in the study. Percentage penetrations at the MPPS were <4.28, <2.22, <0.009 and <0.164 for the N95, FFP2, P100 and FFP3 respirator models, respectively. The MPPS obtained for all four FFR types suggested particle capturing by electrostatic mechanism. Liquid isopropanol treatment of FFRs shifted the MPPS to 200-300 nm and dramatically increased polydisperse as well as monodisperse aerosol penetrations of all four FFR types indicating that all the four FFR types share filtration characteristics of electret filters. Electrostatic charge removal from all four FFR types also increased penetration levels of 400-1000 nm range particles. Particle penetration data obtained in this study showed that the eight models of NIOSH-approved N95 and P100 and CE-marked FFP2 and FFP3 respirators used in this study provided expected levels of laboratory filtration performance against nanoparticles.
Journal of Nanoparticle Research, 2014
The filtration of airborne nanoparticles is an important control technique as the environmental, health, and safety impacts of nanomaterials grow. A review of the literature shows that significant progress has been made on airborne nanoparticle filtration in the academic field in the recent years. We summarize the filtration mechanisms of fibrous and membrane filters; the air flow resistance and filter media figure of merit are discussed. Our review focuses on the air filtration test methods and instrumentation necessary to implement them; recent experimental studies are summarized accordingly. Two methods using monodisperse and polydisperse challenging aerosols, respectively, are discussed in detail. Our survey shows that the commercial instruments are already available for generating a large amount of nanoparticles, sizing, and quantifying them accurately. The commercial self-contained filter test systems provide the possibility of measurement for particles down to 15 nm. Current international standards dealing with efficiency test for filters and filter media focus on measurement of the minimum efficiency at the most penetrating particle size. The available knowledge and instruments provide a solid base for development of test methods to determine the effectiveness of filtration media against airborne nanoparticles down to singledigit nanometer range.
As a precautionary measure, it is often recommended that workers take steps to reduce their exposure to airborne nanoparticles through the use of respiratory protective devices. The purpose of this study was to provide a review and analysis of the research literature and current recommendations on respirators used for protection against nanoparticles. Key research findings were that studies with particles as small as 4 nm have shown that conventional single-fiber filtration theory can be used to describe the filtration performance of respirators and that the most penetrating particle size for respirators equipped with commonly used electrostatic filter media is in the range of 30-100 nm. Future research needs include human laboratory and workplace protection factor studies to measure the respirator total inward leakage of nanoparticles. Industrial hygienists and safety professionals should continue to use traditional respirator selection guidance for workers exposed to nanoparticles.
Particle Count Statistics Applied to the Penetration of a Filter Challenged with Nanoparticles
Aerosol Science and Technology, 2013
Statistical confidence in a single measure of filter penetration (P) is dependent on the low number of particle counts made downstream of the filter. This article discusses methods for determining an upper confidence limit (UCL) for a single measure of penetration. The magnitude of the UCL was then compared to the P value, UCL ≤ 2P, as a penetration acceptance criterion (PAC). This statistical method was applied to penetration trials involving an N95 filtering facepiece respirator challenged with sodium chloride and four engineered nanoparticles: titanium dioxide, iron oxide, silicon dioxide, and single-walled carbon nanotubes. Ten trials were performed for each particle type with the aim of determining the most penetrating particle size (MPPS) and the maximum penetration, P max. The PAC was applied to the size channel containing the MPPS. With those P values that met the PAC for a given set of trials, an average P max and MPPS was computed together with corresponding standard deviations. Because the size distribution of the silicon dioxide aerosol was shifted toward larger particles relative to the MPPS, none of the ten trials satisfied the PAC for that aerosol. The remaining four particle types resulted in at least four trials meeting the criterion. MPPS values ranged from 35 to 53 nm with average P max values varying from 4.0% for titanium dioxide to 7.0% for iron oxide. The use of the PAC is suggested for determining the reliability of penetration measurements obtained to determine filter P max and MPPS.