There has been a significant increase in use of wood pellets in residential and commercial scale boiler systems within New York State, such an increase will lead to increased storage of bulk pellets in homes and buildings. Serious accidents in Europe have been reported over the past decade in which high concentrations of carbon monoxide (CO) have been found in bulk pellet storage bins. Thus, additional exposure data for CO in pellet bin storage areas are needed to assess the potential hazards. Using calibrated CO sensors, continuous CO measurements were made from the spring 2013 to spring 2014 in a number of wood pellet storage bins in New York State. The CO sensors, in some cases, in conjunction with sensors for CO2, O-2, relative humidity, and temperature, were installed in a residential basement, an external storage silo, and several boiler room storage areas in schools and a museum. Peak concentrations in these pellet storage locations ranged from 14 ppm in the basement residence to 155 ppm inside the storage silo at a school. One-hour CO concentrations in the boiler rooms were typically 10-15 ppm. The measured concentrations were compared to regulatory standards of 50 ppm and recommended guidelines of 35 and 9 ppm for work and nonworking environments, respectively. The concentrations at the three locations in the middle school never exceeded the 35 ppm guideline. At the museum, the CO concentrations after pellets delivery did reach a maximum of 55 ppm for a 1-h average. However, high concentrations remained for only 4 days due to natural ventilation in this storage location. Storage areas for pellets must be considered confined spaces and require appropriate entry procedures. As the biomass heating with pellets becomes more prevalent, improved designs for storage bins must be considered to minimize the risk of exposure to CO to building occupants.