YY/T 0866-2024Total inward leakage (TIL) determination method of protective face masks for medical use (English PDF)

4.3 Sodium Chloride Aerosol Generator

4.3.1 Spray liquid The spray liquid is a sodium chloride solution of a certain concentration, generally 2%. The sodium chloride solution is prepared by dissolving reagent-grade sodium chloride in distilled water.

4.3.2 Compressed air supply system The compressed air supply system is used to provide spraying and drying airflows. The compressed air undergoes necessary purification and drying treatment and has sufficient pressure, flow rate and cleanliness. The operating pressure of the aerosol generator is generally approximately

0.7 MPa.

4.3.3 Aerosol generator See Figure 1 for the schematic diagrams of the structure of the aerosol generator. The aerosol is transported to the sealed cabin via a pipeline. The diameter and length of the transportation pipeline shall be large enough to ensure sufficient drying of the aerosol particles, and the radius of the bending parts in the pipeline shall be large enough to reduce particle loss. The air humidity in the sealed cabin shall not exceed 60%. If necessary, the air may be heated or de-humidified. The spray flow rate and pressure of the aerosol generator shall be able to ensure an average mass concentration of sodium chloride aerosol particles within the aerosol sealed cabin of (8 4) mg/m3, with a concentration variation of no more than 10% during the test. The aerodynamic mass median diameter of the sodium chloride aerosol particles shall be between 0.4 m ~ 0.7 m, with a geometric standard deviation of less than 2.0. NOTE. an impactor sampler or particle size spectrometer shall be used to test the aerodynamic diameter of aerosol particles within the cabin.

4.4 Sampling Device

4.4.1 Sampling probe The sampling probe is used to collect aerosol particles within the mask and can be safely fixed to the mask in a sealed manner. The sampling probe material shall be selected to make the probe lightweight. The connecting pipeline between the sampling probe and the testing device shall be flexible, with an inner diameter of 3 mm ~ 4 mm, and the length should not be too long. In addition, the type and length of the sampling pipeline within the cabin shall be the same as those within the mask. When sampling within a mask, in order to reduce sampling bias, a multi-hole sampling probe is preferred (see Figure 2 and Figure 3). If a single-hole sampling probe is selected, design the entrance of the sampling hole as an inclined plane beveled structure (see Figure 4). The sampling probe shall be installed inside the mask close to the subjects' face (< 10 mm), ideally between the mouth and nose (see Figure 5). If necessary, provide support for the sampling probe to avoid deformation of the mask material in the installation area, which may affect the mask's fitness, thereby increasing the total inward leakage. The sampling probe used to collect particles inside the cabin shall be close to the sampling probe inside the mask but avoid being affected by the exhaled gas from the mask.

4.4.2 Sampling flow rate The sampling flow rate generally ranges from

0.1 L/min ~ 2 L/min, depending on the sampling flow rate of the testing device. Set a low sampling flow rate to avoid interference with the protective effect of the mask when worn. The sampling airflow includes a dry airflow, which is used to reduce particle loss due to condensation of sodium chloride particles. This airflow is particularly important for mask products that can generate negative pressure during use. The dry airflow rate is 1 L/min. When the dry airflow is used to dilute the collected particles, the result calculation shall be correspondingly corrected.

4.5.1 Sodium flame photometer

4.5.1.1 Basic principle The sodium flame photometer is a testing device that quantifies the concentration of sodium chloride aerosol particles by testing the intensity of the characteristic combustion spectrum of the element sodium. This method can specifically test sodium chloride particles and is independent of particle size.

4.5.1.2 Parameter requirements The sodium flame photometer must be specifically designed for the testing and analysis of sodium chloride aerosol particles and meet the following requirements.

a) The testing range of sodium chloride aerosol particle concentration shall cover 10 ng/m3 ~ 15 mg/m3;

b) The total sampling flow rate of the photometer shall not exceed 3 L/min;

c) The photometer detector, excluding the sampling module, shall have a full-scale deflection of 10% ~ 90%, and a response time of no more than 500 ms.

4.5.2 Light scattering photometer

4.5.2.1 Basic principle A light scattering photometer is a testing device that irradiates a beam of light onto a particle flow and quantifies aerosol particle concentration by measuring the intensity of the scattered light. This method cannot distinguish between sodium chloride particles and non-sodium chloride particles and has limited detection capabilities for submicron and nanometer-sized particles.

4.5.2.2 Parameter requirements The light scattering photometer shall meet the following requirements.

a) The testing range of sodium chloride aerosol particle concentration shall cover

0.001 mg/m3 ~ 15 mg/m3;

b) The total sampling flow rate of the photometer shall not exceed 4 L/min;