Tao Huai

Dr. Tao Huai is Chief of Freight Emissions Testing and Research Branch in the Mobile Source Laboratory Division at the California Air Resources Board. Dr. Huai has extensive experience working in the field of vehicle emissions research and AB32 GHG regulation development, with nearly 20 years at ARB.  He is currently responsible for conducting comprehensive and unified emissions testing and research programs for heavy-duty trucks and other freight related sources to support CARB’s mobile source regulatory programs and sustainable freight strategies. His scientific contributions include more than two dozen peer-reviewed journal publications and various invited technical presentations. 


  • PhD, Chemical and Environmental Engineering, University of California, Riverside, CA
  • MS, Management Science and Engineering, Tsinghua University, Beijing, China
  • BS, Thermal (Mechanical) Engineering, Tsinghua University, Beijing, China

Areas of Interest

Vehicle Emissions Research and Testing, Environmental Public Policy, Climate Change Mitigation.

Selected Publications

  • Lee, E.S., Sahay, K., O’Neil, E., Biswas, S., Dzhema, I., Huang, S., Lin, P., Chang, M.O., Huai, T., (2023). “Tracer-Gas-Integrated Measurements of Brake-Wear Particulate Matter Emissions from Heavy-Duty Vehicles.” Environmental Science & Technology, 57 (23), pp. 15968–15978.
  • Tan, Y., Yoon, S., Ruehl, C., Herner, J., Henderick, P., Montes, T., Latt, J., Lee, A., Florea, E., Lemieux, S., Robertson, W.H., Hu, S., Huai, T., (2021). “Assessment of In-Use NOx Emissions from Heavy-Duty Diesel Vehicles Equipped with Selective Catalytic Reduction Systems.” Environmental Science & Technology, 55 (20), pp. 13657–13665.
  • Ruehl, C., Misra, C., Yoon, S., Smith J., Burnitzki, M., Hu, S., Collins, J., Tan, Y., Huai, T., Herner, J. (2021).  “Evaluation of Heavy-Duty Vehicle Emission Controls with a Decade of California Real-World Observations.” Journal of the Air & Waste Management Association, 71 (10), pp. 1277-1291.
  • Collet, S., DiCicco, D., Mason, S., Beardsley, M., Berry, N., Long, T., Huai, T., Thornton, M., Purushothaman, R., Shimpi, S., Yoon, S. (2019) “Highlights from the Coordinating Research Council’s 29th Real-World Emissions Workshop.” EM: Air and Waste Management Association's Magazine for Environmental Managers, July.
  • Smith, J.D., Ruehl, C., Burnitzki, M., Sobieralski, W., Ianni, R., Quiros, D.C., Hu, S., Chernich, D., Collins, J., Huai, T., Dwyer, H. (2019). “Real-time particulate emissions rates from active and passive heavy-duty diesel particulate filter regeneration.” Science of the Total Environment, 680, pp. 132–139.
  • Quiros, D.C., Smith, J.D., Ham, W.A., Robertson, W.H., Huai, T., Ayala, A., Hu, S. (2018). “Deriving fuel-based emission factor thresholds to interpret heavy-duty vehicle roadside plume measurements.” Journal of the Air and Waste Management Association, 68(9), pp. 969–987.
  • DiCicco, D., Mason, S., Hogo, H., Purushothaman, R., Huai, T., Herner, J., Shimpl, S., Thornton, M., Back, K., Collet, S., Beardsley, M., Long, T., Tennant, C. (2017). “Highlights from the coordinating research council's 26th real-world emissions workshop.” EM: Air and Waste Management Association's Magazine for Environmental Managers, 67 (January), pp. 40–47.
  • Quiros, D. C., Smith, J., Thiruvengadam, A., Huai, T. and Hu, S. (2017). "Greenhouse Gas Emissions from Heavy-duty Natural Gas, Hybrid, and Conventional Diesel On-road Trucks during Freight Transport." Atmospheric Environment 168: 36-45.
  • Wang, T., Quiros, D. C., Thiruvengadam, A., Pradhan, S., Hu, S., Huai, T., Lee, E. S. and Zhu, Y. (2017). "Total Particle Number Emissions from Modern Diesel, Natural Gas, and Hybrid Heavy-duty Vehicles during On-road Operation." Environmental Science & Technology 51(12): 6990–6998.
  • Xue, J., Li, Y., Quiros, D., Hu, S., Huai, T., Ayala, A. and Jung, H. S. (2017). "Investigation of Alternative Metrics to Quantify PM Mass Emissions from Light Duty Vehicles." Journal of Aerosol Science 113: 85-94.
  • Quiros, D. C., Thiruvengadam, A., Pradhan, S., Besch, M., Thiruvengadam, P., Demirgok, B., Carder, D., Oshinuga, A., Huai, T. and Hu, S. (2016). "Real-world Emissions from Modern Heavy-duty Diesel, Natural Gas, and Hybrid Diesel Trucks Operating along Major California Freight Corridors." Emission Control Science and Technology 2(3): 156-172.
  • Xue, J., Li, Y., Wang, X., Durbin, T. D., Johnson, K. C., Karavalakis, G., Asa-Awuku, A., Villela, M., Quiros, D., Hu, S., Huai, T., Ayala, A. and Jung, H. S. (2015). "Comparison of Vehicle Exhaust Particle Size Distributions Measured by SMPS and EEPS during Steady-State Conditions." Aerosol Science and Technology 49(10): 984-996.
  • Bahreini, R., Xue, J., Johnson, K., Durbin, T., Quiros, D., Hu, S., Huai, T., Ayala, A. and Jung, H. (2015). "Characterizing Emissions and Optical Properties of Particulate Matter from PFI and GDI Light-duty Gasoline Vehicles." Journal of Aerosol Science 90: 144-153.
  • Quiros, D., Yoon, S., Dwyer, H., Collins, J., Zhu, Y.F., Huai, T. (2014) Measuring Particulate Matter Emissions during Parked Active Diesel Particulate Filter Regeneration of Heavy-Duty Trucks. Journal of Aerosol Science. 73, 48–62. 
  • Zheng, Z., Durbin, T.D., Xue, J., Johnson, K.C., Li, Y., Hu, S., Huai, T., Ayala, A., Kittelson, D.B., Jung, H.S. (2014). Comparison of Particle Mass (PM) and Solid Particle Number (SPN) Emissions from a Heavy-Duty Diesel Vehicle under On-Road Driving Conditions and a Standard Testing Cycle. Environmental Science & Technology. 48 (3): 1779–1786. 
  • Hu, S., Zhang, S., Sardar, S., Chen, S.Y., Dzhema, I., Huang, S.M., Quiros, D., Sun, H.W., Laroo, C.A., Sanchez, L.J., Watson, J., Chang, M-C.O., Huai, T., Ayala, A. (2014). Evaluation of Gravimetric Method to Measure Light-duty Vehicle Particulate Matter Emissions at Levels below One Milligram per Mile (1 mg/mile). SAE Tech. Paper 2014-01-1571. 
  • Hu, S., Herner, J.D., Robertson, W., Kobayashi, R., Chang, M-C.O., Huang, S., Zielinska, B., Kado, N., Collins, J., Rieger, P., Huai, T., Ayala, A. (2013). Emissions of Polycyclic Aromatic Hydrocarbons (PAH) and Nitro-PAH Emissions from HDDV with Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR). Journal of the Air & Waste Management Association. 63(8):984–996. 
  • Zheng, Z., Durbin, T.D., Karavalakis, G., Johnson, K.C., Chaudhary, A., Cocker, D.R., Herner, J.D., Robertson, W.H., Huai, T., Ayala, A., Kittelson, D.B., Jung.H.S. (2012). Nature of Sub-23-nm Particles Downstream of the European Particle Measurement Programme (PMP) - Compliant System: A Real-Time Data Perspective. Aerosol Sci. Technol., 46(8):886-896. 
  • Herner, J. D., Hu, S., Robertson, W. H., Huai, T., Chang, M-C. O., Rieger, P., Ayala, A. (2011). Effect of Advanced Aftertreatment for PM and NOx Reduction on Heavy-duty Diesel Engine Ultrafine Particle Emissions. Environmental Science & Technology. 45(6):2413-2419. 
  • Dwyer, H., Ayala, A., Zhang, S., Collins, J., Huai, T., Herner, J., Chau, W. (2010). A Study of Emissions from a Euro 4 Light Duty Diesel Vehicle with the European Particulate Measurement Program. Atmospheric Environment. 44(29), 3469-3476. 
  • Hu, S., Herner, J. D., Shafer, M., Robertson, W., Schauer, J. J., Dwyer, H., Collins, J., Huai, T., Ayala, A. (2009). Metals Emitted from Heavy-duty Diesel Vehicles Equipped with Advanced PM and NOx Emission Controls. Atmospheric Environment. 43(18), 2950-2959. 
  • Durbin, T.D., Miller, J.W., Younglove, T., Huai, T., Cocker, K. (2007). The Effects of Fuel Ethanol Content and Volatility on Regulated and Unregulated Exhaust Emissions for the Latest-Technology Gasoline Vehicles. Environmental Science & Technology, 41 (11), 4059–4064. 
  • Huai, T., Shah, S.D., Miller, W.J., Younglove, T., Chernich, D.J., Ayala, A. (2006). Analysis of Heavy-Duty Diesel Truck Activity and Emissions Data. Atmospheric Environment, 40(13), 2333–2344. 
  • Huai, T., Durbin, T.D., Younglove, T., Scora, G., Barth M., Norbeck, J.M. (2005) Vehicle Specific Power Approach to Estimating On-Road NH3 Emissions from Light-Duty Vehicles. Environmental Science & Technology, 39(24), 9595-9600. 
  • Huai, T., Shah, S.D., Durbin, T.D., Norbeck, J.M. (2005). Measurements of Operational Activity for Nonroad Diesel Construction Equipment. International Journal of Automotive Technology, 6(4), 333-340. 
  • Huai, T., Durbin, T.D., Miller, J.W., Norbeck, J.M. (2004). Estimates of the Emission Rates of Nitrous Oxide from Light-duty Vehicles Using Different Chassis Dynamometer Test Cycles. Atmospheric Environment, 38(38), 6621-6629. 
  • Huai, T., Durbin, T.D., Miller, J.W., Pisano, J.T., Sauer, C.G., Rhee, S.H., Norbeck, J.M. (2003). Investigation of NH3 Emissions from New Technology Vehicles as a Function of Vehicle Operating Conditions. Environmental Science & Technology, 37(21), 4841-4847. 
  • Huai, T., Durbin, T.D., Shee, S.H., Norbeck, J.M. (2003). Investigation of Emission Rates of Ammonia, Nitrous Oxide and Other Exhaust Compounds from Alternative-Fuel Vehicles Using a Chassis Dynamometer. International Journal of Automotive Technology, 4(1), 9-19.