The paper introduces a new type of aerosol sampler designed to collect airborne particles in several categories of decreasing particle size. The sampler, known as the Andersen sampler, is described in detail, including its design, operation, and experimental results. Key features of the sampler include: 1. **Design and Operation**: The sampler is designed to operate at a flow rate of 1 cfm, using a series of stages with decreasing hole sizes to collect particles based on their aerodynamic dimensions. The sampler is made of aluminum alloy with stainless steel fittings and is anodized for corrosion resistance. 2. **Experimental Studies**: - **Wall Loss**: Experiments showed that wall loss is negligible, meaning particles do not stick to the sampler's interior surfaces. - **Slippage**: The sampler effectively prevents slippage of bacterial particles, ensuring all collected particles are viable. - **Sensitivity**: The sampler is highly sensitive, capable of detecting and counting viable particles over a wide range of sizes. - **Particle Size Discrimination**: The sampler can calculate the particle size spectrum of bacterial aerosols, providing valuable data for health hazard assessments. 3. **Applications**: - **Health Hazard Assessment**: The sampler can be used to assess the health hazard in particulate air pollution. - **Pathogenic Organism Detection**: It is useful for detecting and identifying pathogenic organisms, aiding in the control of airborne diseases. - **Other Uses**: The sampler can also collect and analyze various types of particulate matter, including microbial particles, nonviable particles, and radioactive particles. 4. **References and Acknowledgments**: The paper includes references to previous research and acknowledges the contributions of several individuals and organizations. Overall, the Andersen sampler is presented as a reliable and efficient tool for collecting and analyzing airborne particles, particularly for health and safety applications.The paper introduces a new type of aerosol sampler designed to collect airborne particles in several categories of decreasing particle size. The sampler, known as the Andersen sampler, is described in detail, including its design, operation, and experimental results. Key features of the sampler include: 1. **Design and Operation**: The sampler is designed to operate at a flow rate of 1 cfm, using a series of stages with decreasing hole sizes to collect particles based on their aerodynamic dimensions. The sampler is made of aluminum alloy with stainless steel fittings and is anodized for corrosion resistance. 2. **Experimental Studies**: - **Wall Loss**: Experiments showed that wall loss is negligible, meaning particles do not stick to the sampler's interior surfaces. - **Slippage**: The sampler effectively prevents slippage of bacterial particles, ensuring all collected particles are viable. - **Sensitivity**: The sampler is highly sensitive, capable of detecting and counting viable particles over a wide range of sizes. - **Particle Size Discrimination**: The sampler can calculate the particle size spectrum of bacterial aerosols, providing valuable data for health hazard assessments. 3. **Applications**: - **Health Hazard Assessment**: The sampler can be used to assess the health hazard in particulate air pollution. - **Pathogenic Organism Detection**: It is useful for detecting and identifying pathogenic organisms, aiding in the control of airborne diseases. - **Other Uses**: The sampler can also collect and analyze various types of particulate matter, including microbial particles, nonviable particles, and radioactive particles. 4. **References and Acknowledgments**: The paper includes references to previous research and acknowledges the contributions of several individuals and organizations. Overall, the Andersen sampler is presented as a reliable and efficient tool for collecting and analyzing airborne particles, particularly for health and safety applications.