Rock Salt Aerosol Charge Testing Service – Comprehensive Evaluation of Electrostatic Charge, Particle Size Distribution and Aerosol Behaviour for Inhalation Therapy, Environmental Monitoring and Filtration Applications
As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised electric charge testing services for rock salt aerosols (sodium chloride – NaCl) to manufacturers, research institutions, and quality assurance teams across the pharmaceutical, environmental, industrial hygiene, and filtration sectors. Rock salt aerosols – generated by nebulising or dispersing sodium chloride solutions or dry powders – are widely used in inhalation therapy (e.g., saline nebulisation for respiratory conditions), environmental monitoring (as calibration standards for particle counters), and filter testing (as challenge aerosols). The electrostatic charge state of aerosol particles significantly influences their behaviour – including deposition efficiency in the respiratory tract, penetration through filters, and agglomeration and settling rates. Accurate measurement of the net charge and charge distribution of rock salt aerosols is essential for predicting aerosol behaviour, validating nebuliser performance, and ensuring the accuracy of filter efficiency tests. Our test protocols combine electrostatic classification, Faraday cup electrometers, and aerosol characterisation instruments to quantify the charge state, size distribution, and concentration of rock salt aerosols under controlled generation and environmental conditions. All methods are aligned with ISO, ASTM, IEC, and GB/T standards, including ISO 15900 (Differential electrical mobility analysis), ASTM D6060 (Aerosol charge measurement), IEC 61340‑2‑1 (Electrostatic properties), GB/T 16292 (Particle counting), and GB/T 6167 (Particle size distribution). Our inspection and test reports are recognised by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Ecology and Environment (MEE), and international certification bodies for product registration, type approval, and quality assurance.
Rock Salt Aerosol Generation Systems and Samples We Regularly Test
Our aerosol test facilities accommodate a wide range of generation methods and aerosol sample types. Typical test articles include:
- Nebulised rock salt aerosols – from ultrasonic, jet, and vibrating‑mesh nebulisers for inhalation therapy
- Dry powder dispersed rock salt aerosols – from powder dispersion generators and aerosol generators
- Atomised sodium chloride solutions – for calibration and filter testing applications
- Rock salt aerosols from environmental samplers – collected on filters or impactor stages
- Aerosol samples from filtration systems – upstream and downstream for filter efficiency testing
- Nebuliser and aerosol generator performance samples – for quality control and product development
- Pure sodium chloride and rock salt powder – for custom aerosol generation
- Reference aerosols – for instrument calibration and method validation
Charge State Characterisation – Quantifying Aerosol Net Charge and Charge Distribution
- Faraday cup electrometer measurement – ISO 15900 / ASTM D6060 – for measuring the net charge of the aerosol – We collect a known volume of the aerosol on a conductive filter (or an impactor stage) and measure the total charge using a calibrated Faraday cup connected to a high‑sensitivity electrometer (accuracy ±0.1 pA). The net charge (in pC or nC) is divided by the mass (or the number of particles) to obtain the charge‑to‑mass ratio (in µC/g) or the charge‑per‑particle (in elementary charges).
- Differential mobility analysis (DMA) – ISO 15900 / GB/T 16292 – for measuring the charge distribution and the particle size distribution – We use a differential mobility analyser (DMA) to classify the aerosol particles by their electrical mobility (which is a function of the particle size and the charge state). The aerosol is passed through a bipolar charger (to bring the particles to a known equilibrium charge distribution) and then through the DMA. The particles are then counted using a condensation particle counter (CPC) or an electrometer. The DMA‑CPC system provides the particle size distribution (the number concentration as a function of the particle diameter). By comparing the measured size distribution with the size distribution measured without the electrostatic classifier, we can determine the charge distribution.
- Electrostatic precipitator (ESP) collection efficiency test – for assessing the charge state of the aerosol – We pass the aerosol through a high‑voltage electrostatic precipitator (ESP) and measure the collection efficiency (the percentage of particles collected) as a function of the applied voltage. The ESP collection efficiency is a measure of the aerosol's charge state. A high collection efficiency (> 90 %) indicates a highly charged aerosol; a low collection efficiency (< 20 %) indicates a neutral aerosol.
- Penetration through charged filters – for assessing the effect of charge on filtration efficiency – We pass the aerosol through a charged filter (or a conductive filter) and measure the particle concentration upstream and downstream of the filter. The penetration (the ratio of the downstream concentration to the upstream concentration) is a measure of the filter's ability to capture charged particles. The test is performed with the filter at different charging voltages (to simulate different environmental conditions).
- Charge measurement using an aerosol electrometer – for real‑time monitoring of the aerosol charge – We use a real‑time aerosol electrometer (e.g., a Faraday cage aerosol electrometer) to measure the net charge of the aerosol as it flows through the instrument. The electrometer provides the total current (in pA) and the charge concentration (in C/m³). The test is performed at different aerosol flow rates and at different generation conditions.
Particle Size Distribution and Concentration Measurement – Characterising the Aerosol
- Particle size distribution using an aerodynamic particle sizer (APS) – ISO 15900 / GB/T 6167 – for measuring the aerodynamic diameter – We use an aerodynamic particle sizer (APS) to measure the aerodynamic diameter (in µm) and the number concentration (in particles/cm³) of the rock salt aerosol. The APS operates on the principle of time‑of‑flight measurement, which is not affected by the electrostatic charge. The size distribution is used as the baseline for the charge state assessment.
- Particle size distribution using an optical particle counter (OPC) – for measuring the optical diameter – We use an optical particle counter (OPC) to measure the optical diameter (in µm) and the number concentration (in particles/cm³) of the aerosol. The OPC measures the scattering of light by the particles. The optical diameter is a function of the particle's refractive index and the wavelength of the light. The OPC is sensitive to the particle size, but it is not affected by the charge state.
- Particle size distribution using a scanning mobility particle sizer (SMPS) – ISO 15900 / GB/T 16292 – for measuring the electrical mobility diameter – We use a scanning mobility particle sizer (SMPS), which consists of a DMA and a CPC, to measure the electrical mobility diameter (in nm) and the number concentration (in particles/cm³). The SMPS provides the size distribution of the particles based on their electrical mobility. The charge state of the particles affects the measured size distribution; therefore, the SMPS measurement is used in conjunction with the charge state assessment.
- Mass concentration measurement – using gravimetric analysis – ISO 9096 / GB/T 16157 – for measuring the mass concentration – We collect the aerosol on a pre‑weighed filter and weigh the filter after the collection. The mass concentration (in mg/m³) is calculated from the mass increase and the sampled volume. The gravimetric method is independent of the aerosol charge state.
Environmental and Generation Conditions – Simulating Service Conditions
- Humidity‑conditioned charge testing – for assessing the effect of humidity on the charge state – We generate the rock salt aerosol at different humidity levels (e.g., 10 % RH, 50 % RH, 90 % RH) using a humidity‑controlled aerosol generation system. The charge state of the aerosol is measured at each humidity level. The test assesses the effect of humidity on the charge generation and the charge dissipation.
- Temperature‑conditioned charge testing – for assessing the effect of temperature on the charge state – We generate the rock salt aerosol at different temperatures (e.g., 20 °C, 40 °C, 60 °C) using a temperature‑controlled aerosol generation system. The charge state of the aerosol is measured at each temperature. The test assesses the effect of temperature on the charge generation and the charge dissipation.
- Generation parameter variation – for assessing the effect of nebuliser and generator settings on the charge state – We vary the generation parameters (e.g., the liquid flow rate, the gas flow rate, the ultrasonic power, the voltage applied to the atomiser) and measure the resulting charge state. The test is used to optimise the generation conditions for a specific application.
- Ageing and storage test – for assessing the effect of aerosol ageing on the charge state – We store the generated aerosol in a sample bag (or a chamber) for a specified period (e.g., 1‑24 hours) and then measure the charge state. The test assesses the effect of ageing (coagulation, evaporation, and charge neutralisation) on the aerosol charge state.
Regulatory Compliance and Product Certification – Supporting Industry Standards
Our rock salt aerosol charge testing services are performed in accordance with the most widely used international and national standards. The most commonly requested include:
- ISO 15900 – Determination of particle size distribution – Differential electrical mobility analysis for aerosol particles – the primary standard for aerosol charge and size measurement
- ASTM D6060 – Standard Test Method for Measuring the Charge on an Aerosol – for aerosol charge measurement
- IEC 61340‑2‑1 – Electrostatic properties – Part 2‑1: Test methods for measuring the charge of objects – for electrostatic charge measurement
- GB/T 16292 – Particle counting – Determination of particle size distribution – the Chinese national standard for particle size measurement
- GB/T 6167 – Particle size distribution – Determination of particle size distribution using an optical particle counter – the Chinese national standard for particle counting
- ISO 9096 – Stationary source emissions – Manual determination of mass concentration of particulate matter – for gravimetric measurement
- ISO 28439 – Workplace atmospheres – Determination of ultrafine aerosol – for ultrafine aerosol measurement
- GB/T 16157 – Determination of particulates in the gas from stationary sources – the Chinese national standard for particulate measurement
Report Acceptance and Regulatory Recognition
All rock salt aerosol charge tests are conducted under our ISO/IEC 17025 accreditation, using calibrated aerosol generators, electrometers, and particle counters, all traceable to national and international reference standards. Our final test reports include: a complete description of the aerosol generation system and the test conditions (temperature, humidity, flow rate), the measured parameters (charge‑to‑mass ratio, charge distribution, particle size distribution, concentration), a statistical summary (mean, standard deviation, coefficient of variation), and a clear pass/fail verdict against your specified acceptance criteria. These reports are accepted by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Ecology and Environment (MEE), and international certification bodies for product registration, type approval, and quality assurance. Bilingual (English/Chinese) versions are available to facilitate submissions to domestic and international authorities and to support your global market access.
