Some  plant emissions are made up of terpenes, thiols, and other compounds. Terpenes, or Biogenic Volatile Organic Compounds (BVOCs), have no public health impact when breathed in. BVOCs, when mixed with sunlight and reactions with other combustion emissions, can cause the formation of ozone and particulate matter (PM). The determination of impact to air quality from commercial cultivation is highly dependent upon the amount of emissions from combustion sources and the meteorological conditions in the proposed environment. For example, the urban areas of Denver, Colorado, and British Columbia, Canada, have large combustion sources but relatively little in the amount of BVOCs that are available. Thus, these areas are known as VOC-limited and in these circumstances BVOCs being emitted from large-scale crop cultivation have the potential to form ozone and PM. The proper identification and measurement of plant emissions, coupled with air quality models, can help determine the extent of impact and guide the best possible control technologies. These technologies can mitigate these emissions before they reach the ambient air and significantly reduce the potential negative impacts to human health.