Nanoparticle Emission Assessment Technique - NEAT

The National Institute for Occupational Safety and Health ("NIOSH") established a field research team that has developed a nanoparticle emission assessment technique ("NEAT") uses a combination of measurement techniques and instruments to assess potential inhalation exposures in facilities that handle engineered nanomaterials. "The NEAT employs a combination of direct-reading, handheld instruments (CPC and OPC) to detect releases of airborne nanomaterial coupled with filter-based air sampling and subsequent chemical and microscopic analyses for particle identification and chemical speciation." ¹

• Instrumentation and Materials²
   
  • Condensation Particle Counter (CPC) - The team utilized a "handheld CPC that operates by drawing in air, passing it through a heated saturator filled with isopropylalcohol, and then cooling the airstream via a condenserchamber. . . . The data output is expressed as total number of particles per cubic centimeter of air (1/cm3) with an upper dynamic range limit of approximately 100,000 1/cm3. The value of this instrument for evaluating nanomaterial emissions is its ability to detect particles in the 10 to 100 nm range (the current definition of a nanomaterial), even though it will respond to the presence of larger particles. A limitation of this instrument is that it cannot accurately quantify particles below the 10 nm threshold."³
     
  • Optical Particle Counter (OPC) - The team utilized a OPC "to determine the number concentration of particles based on optical counting principles using laser light scattering (ART Instruments). This instrument measures the total number of particles per liter of air (1/L) according to six specific size cutpoints: 300 nm, 500 nm, 1000 nm, 3000 nm, 5000 nm, and 10,000 nm."⁴

• Air Sampling Filter Media - "Appropriate air sampling filter media are selected based on the engineered nanomaterial type and desired analytical information (e.g., chemical composition determination of particlemass concentration, elemental analysis, particle morphologyusing transmission electron microscopy (TEM) or scanning electron microscopy (SEM)). Air sampling pumps capable of relatively high flow rates (e.g., 7 L/min or other flow rate depending on the duration of the task, pressure drop due to different filter media, and the appropriate NIOSH analytical method, if one is available) are used to collect the filter samples."⁶

• Sampling Strategy
  • Identify Potential Sources of Emissions
  • Conduct Particle Number Concentration Sampling
  • Collect Filter-Based Samples