Aerodynamic Size Distribution Research Articles

Comparative performance study of paperboard disposable spacers versus commercial valved holding chambers for aerosol delivery

PurposeThe aim of this study is to evaluate and compare the performance, for the administration of fluticasone propionate with a pressurized metered-dose inhaler (pMDI), of two low-tech paperboard spacers versus two commercially available valved holding chambers (VHC). MethodsAccording to the Canadian standard CAN/CSA-Z264.1–02, total emitted dose (TED) and aerodynamic size distribution were measured for the pMDI in combination with 4 different spacers: a homemade paper cup spacer, the DispozABLE® paperboard spacer, the AeroChamber Plus® plastic VHC, and the Vortex® aluminium VHC. ResultsThe two disposable paperboard spacers had a lower TED compared to the aluminium VHC, but delivered more than 2.5 times the dose of fluticasone than the commercial plastic VHC. The 3 antistatic devices (i.e. the aluminium VHC, the paperboard DispozABLE® spacer and the paper cup spacer) delivered a significantly higher dose of fine particles than the less antistatic plastic VHC. Their fine particle fraction was statistically similar to that obtained with pMDI without spacer. This respirable fraction ensures an optimal therapeutic effect. All spacers limited the flow of coarse particles, thus avoiding adverse effects on the trachea and oropharynx. ConclusionWe have shown that inexpensive and low-tech paperboard spacers are interesting alternatives for the administration of aerosols.

Evaluation of coating materials on the characterization of size and viability of virus-laden particles collected with an Andersen cascade impactor

Airborne pathogens are typically associated with particles, and the transport behavior of these particles is largely driven by their size. To better understand airborne transmission of viral diseases and develop effective control measures, proper size characterization of virus-laden particles is essential. The Andersen cascade impactor (ACI) is an 8-stage air sampler that separates aerosol particles into 9 aerodynamic size fractions. During sampling with an ACI under certain conditions, particles may bounce upon impact with the collection plates of the ACI, leading to eventual deposition on a stage further downstream than their target stage. Coating collection plates with adhesive materials may help decrease particle bounce; however, it may also affect the viability of collected pathogens. In this study, we evaluated different materials for their ability to minimize particle bounce while conserving virus viability during the collection of viral aerosol particles with an ACI. We evaluated nine materials - Tween® 80, silicone oil, Span® 85, Brij® 35, glycerol, mineral oil, gelatin, bovine serum albumin, and virus growth media - on their effect to inactivate H1N1 influenza virus and bovine coronavirus, a surrogate of SARS-CoV-2. Plates coated with gelatin, silicone oil, and mineral oil resulted in the least reduction of viability for both viruses. These materials were then used to sample viral aerosol particles in a wind tunnel. Results of physical particle collection, viral load and viral viability from the various ACI stages revealed no significant differences in aerodynamic size distribution between coated and uncoated plates, and the size distribution was similar to that reported by an optical particle sizer. Overall, our results did not support the need to coat ACI collection plates when characterizing viral aerosol particles under the conditions of this study. However, we did identify potential coating materials which could conserve virus viability maximally, if particle bounce is of concern.

347 Aerodynamic Size Distribution of SARS-CoV-2 Aerosol Shedding

OBJECTIVES/GOALS: We designed the Biocascade Exhaled Breath Sampler (BEBS) to characterize viral aerosol shedding among individuals with influenza and other respiratory virus infections. We first aimed to test the BEBS on volunteer COVID-19 cases and report the aerodynamic size distribution of exhaled breath aerosol particles carrying SARS-CoV-2 RNA. METHODS/STUDY POPULATION: From June 15 through December 15, 2022, we recruited 27 PCR-confirmed COVID-19 cases from a college campus and the surrounding community to provide 30-minute breath samples into a well-validated Gesundheit-II (G-II) exhaled breath aerosol sampler. Among these individuals, 17 provided an additional exhaled breath sample into the newly designed BEBS. We quantified samples for viral RNA using reverse transcription digital polymerase chain reaction (RT-dPCR) and determined the viral RNA copies collected within two aerosol size fractions (≤5 µm and >5 µm in diameter) from the G-II, and four aerosol size fractions (<1.15 µm, 1.15–3.2 µm, 3.3–8.2 µm, and >8.2 µm) from the BEBS. RESULTS/ANTICIPATED RESULTS: Individuals with a SARS-CoV-2 Omicron BA.4 or BA.5 infection shed virus in aerosols at an average rate of 7.5x103 RNA copies per 30-minute G-II sample, with 78% of the total RNA in aerosols ≤5 µm in diameter. Among the BEBS samples, 10% of the total viral RNA was detected in aerosols <1.15 µm, 43% in 1.15–3.2 µm, 37% in 3.3–8.2 µm, and 10% in the >8.2 µm size fraction. Based on viral RNA loads, our results indicate that exhaled aerosols ≤3.2 µm contribute the majority of SARS-CoV-2 inhalation exposure. DISCUSSION/SIGNIFICANCE: Our data provide additional evidence that respirable aerosols contribute to the spread of SARS-CoV-2. Thus, our data suggest that mitigation measures designed to reduce infectious aerosol inhalation, such as ventilation and the use of air cleaners and respirators, are needed to control the spread.

Abstracts from The Aerosol Society Drug Delivery to the Lungs 33.

Abstracts from The Aerosol Society Drug Delivery to the Lungs 33.

A novel particle engineering method for the production of inhalable cromolyn sodium powders by a combination of spray drier and nebulizer

Cromolyn sodium is a promising treatment for respiratory disease, especially asthma. Cromolyn sodium is mostly used in the form of a dry powder inhaler (DPI). Morphology of the powder, particle size, dispersibility, and stability are features that greatly influence the absorption efficiency of the given formulation and can be controlled through particle engineering. Although spray drying is the most common production method of cromolyn sodium, this method has some drawbacks including wide droplet size distribution, clogging risk, and lack of direct control over the mean droplet size. To enhance the aerosol performance of the powder, a new method known as a nebulizer-spray drier coupling (NSD) is proposed which affects the particle size distribution, surface features, and aerodynamic properties of the formulation. Ammonium bicarbonate and ethanol were added to assess the variation of produced powder porosity. The morphology, surface and crystallographic features of particles were analyzed with scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET, and X-ray diffraction (XRD) techniques respectively. Aerosol performance was measured with the next generation impactor (NGI). The results show that unlike the needle-like particle shape of the commercial (CS) cromolyn sodium and untreated (raw) cromolyn sodium, the NSD samples have a mushroom-like and spherical particle shape. In the same condition, NSD samples show higher fine particle fraction (FPF) and lower aerodynamic size distribution compared to their counterpart samples (spray-dried). The amorphous structure of the generated powder was confirmed through XRD and DSC analysis. Also, the addition of ammonium bicarbonate produced wider size distribution for particles, providing spherical, hollow, smooth-surface particles. Moreover, the influence of using ethanol (in spray drying process) as a solvent was explored, where the aerosolization performance was found to be improved when ethanol was added to the spray dried solutions. It was concluded that the newly developed powder preparation method (NSD method) could successfully provide cromolyn sodium powder for inhalation and can be introduced as a novel technique for particle engineering of DPIs.

Aerosol mass and size-resolved metal content in urban Bangkok, Thailand

Inhalable particulate matter (PM) is a health concern, and people living in large cities such as Bangkok are exposed to high concentrations. This exposure has been linked to respiratory and cardiac diseases and cancers of the lung and brain. Throughout 2018, PM was measured in northern Bangkok near a toll road (13.87°N, 100.58°E) covering all three seasons (cool, hot and rainy). PM10 was measured in 24- and 72-h samples. On selected dates aerodynamic size and mass distribution were measured as 3-day samples from a fixed 5th floor inlet. Particle number concentration was measured from the 5th floor inlet and in roadside survey measurements. There was a large fraction of particle number concentration in the sub-micron range, which showed the greatest variability compared with larger fractions. Metals associated with combustion sources were most found on the smaller size fraction of particles, which may have implications for associated adverse health outcomes because of the likely location of aerosol deposition in the distal airways of the lung. PM10 samples varied between 30 and 100 μg m−3, with highest concentrations in the cool season. The largest metal fractions present in the PM10 measurements were calcium, iron and magnesium during the hot season with average airborne concentrations of 13.2, 3.6 and 2.0 μg m−3, respectively. Copper, zinc, arsenic, selenium, molybdenum, cadmium, antimony and lead had large non-crustal sources. Principal component analysis (PCA) identified likely sources of the metals as crustal minerals, tailpipe exhaust and non-combustion traffic. A health risk analysis showed a higher risk of both carcinogenic and non-carcinogenic health effects in the drier seasons than the wet season due to ingestion of nickel, arsenic, cadmium and lead.Graphical abstract

Differentiation of coarse-mode anthropogenic, marine and dust particles in the High Arctic islands of Svalbard

Abstract. Understanding aerosol–cloud–climate interactions in the Arctic is key to predicting the climate in this rapidly changing region. Whilst many studies have focused on submicrometer aerosol (diameter less than 1 µm), relatively little is known about the supermicrometer aerosol (diameter above 1 µm). Here, we present a cluster analysis of multiyear (2015–2019) aerodynamic volume size distributions, with diameter ranging from 0.5 to 20 µm, measured continuously at the Gruvebadet Observatory in the Svalbard archipelago. Together with aerosol chemical composition data from several online and offline measurements, we apportioned the occurrence of the coarse-mode aerosols during the study period (mainly from March to October) to anthropogenic (two sources, 27 %) and natural (three sources, 73 %) origins. Specifically, two clusters are related to Arctic haze with high levels of black carbon, sulfate and accumulation mode (0.1–1 µm) aerosol. The first cluster (9 %) is attributed to ammonium sulfate-rich Arctic haze particles, whereas the second one (18 %) is attributed to larger-mode aerosol mixed with sea salt. The three natural aerosol clusters were open-ocean sea spray aerosol (34 %), mineral dust (7 %) and an unidentified source of sea spray-related aerosol (32 %). The results suggest that sea-spray-related aerosol in polar regions may be more complex than previously thought due to short- and long-distance origins and mixtures with Arctic haze, biogenic and likely blowing snow aerosols. Studying supermicrometer natural aerosol in the Arctic is imperative for understanding the impacts of changing natural processes on Arctic aerosol.

A generic fluticasone propionate and salmeterol dry powder inhaler: Evidence of usability, function, and robustness.

Background: A generic combination of fluticasone propionate and salmeterol xinafoate inhalation powder in a premetered, multidose, nonreusable inhaler was recently approved. Objective: To assess the performance of the generic device. Methods: Findings from three studies with regard to device usability, function, and robustness were reviewed. Results: In a study to assess device function in patients and healthy volunteers, the generic device was successfully used by patients with asthma and chronic obstructive pulmonary disease who were either dry powder inhaler users or dry powder inhaler-naive, even though they were not trained beyond being provided the instructions for use. In a study to measure inhaled flow rates generated by patients and healthy volunteers, the generic device consistently simulated the delivery of a full dose of drug, even to patients with severe respiratory disease and reduced inspiratory flow rates. Although the generic device had a slightly higher airflow resistance, this study demonstrated that this difference did not result in any clinically meaningful differences in terms of drug delivery. Pressure drop, a key parameter that drives the fluidization and aerosolization of the powder dose, was found to be comparable between the devices. In an open-label study, the generic device met all U.S. Food and Drug Administration specifications for device robustness after 21.5 days of twice-daily dosing via oral inhalation among 111 participants with asthma or chronic obstructive pulmonary disease. All inhalers tested demonstrated conformity with a pharmacopeia with respect to key quality parameters (assay, delivered dose uniformity, aerodynamic size distribution). There was no evidence of chemical degradation of the active ingredients, nor of microbial or water ingress into the powder, as a result of inhaler use.

Accelerated measurements of aerosol size distributions by continuously scanning the aerodynamic aerosol classifier

Using an Aerodynamic Aerosol Classifier (AAC) upstream of a particle detector is a relatively new method for measuring the aerodynamic size distribution of an aerosol. This approach overcomes limit...

Simple Method to Measure the Aerodynamic Size Distribution of Porous Particles Generated on Lyophilizate for Dry Powder Inhalation.

Recently, statistical techniques such as design of experiments are being applied for efficient optimization of oral formulations. To use these statistical techniques for inhalation formulations, efficient methods for rapid determination of the aerodynamic particle size distribution of many samples are needed. Therefore, we aimed to develop a simple method to measure aerodynamic particle size distribution that closely agrees with the results of inhalation characteristic tests. We added attachments for dispersion to the aerodynamic particle sizer (APS) so that formulations could be dispersed under the same condition as for multi-stage liquid impinger (MSLI) measurement. Then, we examined the correlation between MSLI and APS using lyophilizate for dry powder inhalation formulations that generate porous particles just on inhalation. It is difficult to obtain the accurate aerodynamic particle size distribution of porous particles by APS because the particle density is difficult to estimate accurately. However, there was a significant correlation between MSLI and APS when the particle density settings for APS measurement was calculated by a conversion factor based on the result of MSLI. The APS with dispersion attachments and this conversion factor can measure a number of samples in a short time, thereby enabling more efficient optimization of dry powder inhalers.

Nebulised Gadolinium-Based Nanoparticles for a Multimodal Approach: Quantitative and Qualitative Lung Distribution Using Magnetic Resonance and Scintigraphy Imaging in Isolated Ventilated Porcine Lungs.

PurposeThis study aims at determining lung distribution of gadolinium-based polysiloxane nanoparticles, AGuIX® (small rigid platform – SRP), as a potential theranostic approach by the pulmonary route.MethodsFirst, the aerodynamic size distribution and the aerosol output rate were thoroughly characterized. Then, a multimodal approach using magnetic resonance (MR) and gamma-camera (GC) imaging allows to assess the deposition of the aerosolised nanoparticles in the respiratory tract using isolated ventilated porcine lungs.ResultsThe SRP has proven to be radiolabelled by radioisotope with a good yield. Crude SRP or radiolabelled ones showed the same aerodynamic size distribution and output as a conventional molecular tracer, as sodium fluoride. With MR and GC imaging approaches, the nebulised dose represented about 50% of the initial dose of nanoparticles placed in the nebuliser. Results expressed as proportions of the deposited aerosol showed approximately a regional aerosol deposition of 50% of the deposited dose in the lungs and 50% in the upper airways. Each technique assessed a homogeneous pattern of deposited nanoparticles in Lungs. MR observed a strong signal enhancement with the SRP, similar to the one obtained with a commonly used MRI contrast agent, gadoterate meglumine.ConclusionAs a known theranostic approach by intravenous administration, SRP appeared to be easily aerosolised with a conventional nebuliser. The present work proves that pulmonary administration of SRP is feasible in a human-like model and allows multimodal imaging with MR and GC imaging. This work presents the proof of concept of SRP nebulisation and aims to generate preclinical data for the potential clinical transfer of SRP for pulmonary delivery.

A valuable experimental setup to model exposure to Legionella’s aerosols generated by shower-like systems

The mechanism underlying Legionella aerosolization and entry into the respiratory tract remains poorly documented. In previous studies, we characterized the aerodynamic behaviour of Legionella aerosols and assessed their regional deposition within the respiratory tract using a human-like anatomical model. The aim of this study was to assess whether this experimental setup could mimic the exposure to bioaerosols generated by showers. To achieve this objective we performed experiments to measure the mass median aerodynamic diameter (MMAD) as well as the emitted dose and the physiological state of the airborne bacteria generated by a shower and two nebulizers (vibrating-mesh and jet nebulizers). The MMADs of the dispersed bioaerosols were characterized using a 12-stage cascade low-pressure impactor. The amount of dispersed airborne bacteria from a shower was quantified using a Coriolis® Delta air sampler and compared to the airborne bacteria reaching the thoracic region in the experimental setup. The physiological state and concentration of airborne Legionella were assessed by qPCR for total cells, culture for viable and cultivable Legionella (VC), and flow cytometry for viable but non-cultivable Legionella (VBNC). In summary, the experimental setup developed appears to mimic the bioaerosol emission of a shower in terms of aerodynamic size distribution. Compared to the specific case of a shower used as a reference in this study, the experimental setup developed underestimates by 2 times (when the jet nebulizer is used) or overestimates by 43 times (when the vibrating-mesh nebulizer is used) the total emitted dose of airborne bacteria. To our knowledge, this report is the first showing that an experimental model mimics so closely an exposure to Legionella aerosols produced by showers to assess human lung deposition and infection in well-controlled and safe conditions.

Integrated Continuous Plug-Flow Crystallization and Spray Drying of Pharmaceuticals for Dry Powder Inhalation

The manufacture of dry powders for pulmonary drug delivery is complicated by stringent requirements for the aerodynamic size distribution and solid-state properties of the powder. Micronization is often needed after conventional batch crystallization to reduce the particle size, which lowers the process yield and may lead to particles with poor aerosolization behavior. A novel process combining continuous plug-flow crystallization and spray drying is presented to produce crystals with optimal properties for pulmonary drug delivery in a single step. Continuous flow enables fast nucleation with antisolvent crystallization. Subsequently, the narrow and controllable residence time distribution of segmented-flow crystallization is exploited to grow the crystals uniformly into the optimal size range for pulmonary drug delivery. Finally, the solvent is evaporated rapidly using spray drying in a continuous flow. Two case studies involving relevant drugs for pulmonary delivery are presented to demonstrate practical relevance and process flexibility. The process can be optimized for both cases such that a dry powder with excellent aerosolization behavior is produced. The novel process is simple and flexible due to the clear separation of process functions and the availability of sufficient process variables for optimization.

On the Effective Density and Fractal–Like Dimension of Diesel Soot Aggregates as a Function of Mobility Diameter

A new technique is proposed for the assessment of aggregate morphology based on combined information of aerodynamic and mobility size distributions. Instead of formulating a complex inverse problem having aggregate morphology as unknown, the actual problem is separated to two stages. The aerodynamic distribution is determined directly by the electric low pressure impactor (ELPI) data whereas the morphology is independently assessed by matching the distribution arises from ELPI and from scanning mobility particle sizer (SMPS). The advantage of this approach is that it can estimate different fractal dimension for different aggregate size. The approach is applied to soot aggregates from three different diesel engines. In all cases, a non-monotonic behavior of fractal dimension versus aggregate size is observed. In particular, the fractal dimension initially decreases and then increases (passing through a minimum) as the mobility diameter increases.

Effective density of airborne particles in a railway tunnel from field measurements of mobility and aerodynamic size distributions

The objective of this study is to investigate the particle effective density of aerosol measurements in a railway tunnel environment. Effective density can serve as a parameter when comparing and c...

Continuous dry dispersion of multi-walled carbon nanotubes to aerosols with high concentrations of individual fibers

The assessment of the toxicity of airborne nanofibers is an important task. It relies on toxicological inhalation studies and validated exposure measurement techniques. Both require nanofiber-containing aerosols of known morphological composition and controlled fraction of individual fibers. Here, a dry powder dispersion method is presented that operates with mixtures of nanofibers and microscale beads. Aerosolization experiments of mixtures of multi-walled carbon nanotubes (MWCNTs) and glass beads that were continuously fed into a Venturi nozzle enabled high generation rates of aerosols composed of individual and agglomerate nanofiber structures. The aerosol process achieved good stability over more than 2 h with respect to concentration and aerodynamic size distribution. Its operation duration is limited only by the reservoir volume of the cyclone used to separate the beads from the aerosol. The aerosol concentration can be controlled by changing the mass ratio of MWCNTs and glass beads or by adapting the mass feed rate to the nozzle. For two agglomerated MWCNT materials, aerosol concentrations ranged from 1700 to 64,000 nano-objects per cm3. Comprehensive scanning electron microscope analysis of filter samples was performed to categorize and determine the morphological composition of the aerosol, its fiber content as well as fiber length and diameter distributions. High fractions of individual fibers of up to 34% were obtained, which shows the setup to be capable of dispersing also highly tangled MWCNT agglomerates effectively.

In Vitro Characterization of the eFlow Closed System Nebulizer with Glycopyrrolate Inhalation Solution.

Background: Glycopyrrolate administered by a novel, investigational eFlow® Closed System (CS) nebulizer (eFlow CS) is being evaluated for the maintenance treatment of chronic obstructive pulmonary disease (COPD). The eFlow CS is a hand-held, vibrating membrane nebulizer optimized to deliver 1 mL of glycopyrrolate solution into the lung in <3 minutes. Clinical studies have shown improvements in lung function of subjects treated with nebulized glycopyrrolate.Methods: The aerosol performance of the eFlow CS nebulizer was characterized by delivered dose, aerodynamic droplet size distribution and nebulization time. Simulated use nebulizer performance over 60 days was assessed by volume median diameter (VMD), nebulized amount, and nebulization time. Nebulization outputs were assayed to ensure adequate delivery of glycopyrrolate with an acceptable impurity profile. Aerosol condensates were analyzed for glycopyrrolate concentration and impurities by ultra-high-performance liquid chromatography and compared with non-nebulized samples.Results: The mean mass median aerodynamic diameter, geometric standard deviation, and fine particle fraction were 3.7 μm, 1.7, and 72%, respectively, and independent of formulation strength (25 and 50 μg/mL). Delivered dose was 88% of the nominal dose for both formulation strengths. The mean delivered dose, assessed by breathing simulation, was 56.8% for 25 μg/mL and 62.6% for 50 μg/mL. Nebulization times were 1–2.5 minutes with no apparent increasing trend with use over a 60-day period. The nebulized amount showed no significant changes, whereas the VMD showed a slight, but not pharmaceutically relevant, increase (0.1–0.2 μm) after 60-day simulated use. Glycopyrrolate concentration and impurity levels of nebulized samples were statistically similar to those of non-nebulized samples.Conclusion: The eFlow CS generates glycopyrrolate aerosols with high delivered dose, short treatment time, and small droplet size with narrow size distribution suitable for central and peripheral airway deposition. The unit dose vial mitigates medication misuse and ensures dose uniformity. Results support the use of glycopyrrolate/eFlow CS for the treatment of COPD.

The characterization of surgical smoke from various tissues and its implications for occupational safety.

Electrosurgery produces surgical smoke. Different tissues produce different quantities and types of smoke, so we studied the particle characteristics of this surgical smoke in order to analyze the implications for the occupational health of the operation room personnel. We estimated the deposition of particulate matter (PM) from surgical smoke on the respiratory tract of operation room personnel using clinically relevant tissues from Finnish landrace porcine tissues including skeletal muscle, liver, subcutaneous fat, renal pelvis, renal cortex, lung, bronchus, cerebral gray and white matter, and skin. In order to standardize the electrosurgical cuts and smoke concentrations, we built a customized computer-controlled platform. The smoke particles were analyzed with an electrical low pressure impactor (ELPI), which measures the concentration and aerodynamic size distribution of particles with a diameter between 7 nm and 10 μm. There were significant differences in the mass concentration and size distribution of the surgical smoke particles depending on the electrocauterized tissue. Of the various tissues tested, liver yielded the highest number of particles. In order to better estimate the health hazard, we propose that the tissues can be divided into three distinct classes according to their surgical smoke production: 1) high-PM tissue for liver; 2) medium-PM tissues for renal cortex, renal pelvis, and skeletal muscle; and 3) low-PM tissues for skin, gray matter, white matter, bronchus, and subcutaneous fat.

Measuring aerosol size distributions with the aerodynamic aerosol classifier

ABSTRACTThe Aerodynamic Aerosol Classifier (AAC) is a novel instrument that selects aerosol particles based on their relaxation time or aerodynamic diameter. Additional theory and characterization is required to allow the AAC to accurately measure an aerosol’s aerodynamic size distribution by stepping while connected to a particle counter (such as a Condensation Particle Counter, CPC). To achieve this goal, this study characterized the AAC transfer function (from 32 nm to 3 μm) using tandem AACs and comparing the experimental results to the theoretical tandem deconvolution. These results show that the AAC transmission efficiency is 2.6–5.1 times higher than a combined Krypton-85 radioactive neutralizer and Differential Mobility Analyzer (DMA), as the AAC classifies particles independent of their charge state. However, the AAC transfer function is 1.3–1.9 times broader than predicted by theory. Using this characterized transfer function, the theory to measure an aerosol’s aerodynamic size distribution usin...

Effective density of airborne wear particles from car brake materials

People living in urban environments are subject to high health risks due to various anthropogenic sources of airborne particulate matter, including wear of transport vehicle brakes. Studies of airborne particles often require an estimate of the effective particle density, a property that allows correct matching of mass and size characteristics measured by different aerosol instruments. In this study we investigated the effective density of airborne wear particles emitted from car brake materials. The particles were generated by a pin-on-disc machine located in a sealed chamber. Two methods were used to determine the effective density. The first method is based on measurements of PM10 and particle size distribution. The second method involves measurements and subsequent fitting of the mobility size distribution and aerodynamic size distribution. Results from the two methods showed good agreement. It was found that the effective density is 0.75±0.2g/cm3. The particle emission, size distribution and effective density are sensitive to temperature variations. An intensive emission of ultrafine particles is initiated at the disc temperature of 185±16°C. The effective density decreases with the temperature in the interval 110–360°C. There is a large difference between the effective density and the density of the particle material, which suggests that the particles are porous.