OSHA 3763-12 2014 - Hydraulic fracturing is a treatment process that stimulates well production in the upstream oil and gas industry. While not a new process, hydraulic fracturing has been increasingly used in the last ten years due to the increase in horizontal well development, which requires multiple stimulation stages per well. Hydraulic fracturing involves pumping large volumes of fluid blended with proppant and chemicals at pressures necessary to fracture a hydrocarbon-containing formation. Once the fractures are created, proppants are placed within the fractures to hold them open and allow for the release and flowback of fluids and hydrocarbons. Each year, an estimated 35,000 wells are hydraulically-fractured in the U.S. Although the oil and gas extraction industry as a whole has a relatively higher fatality rate compared to most of the U.S. general industry, there is currently no worker injury/illness or fatality data publicly available for hydraulic fracturing or flowback operations. Regardless of the availability of data, more workers are potentially exposed to the hazards created by hydraulic fracturing and flowback operations due to the large increase in the number of these operations in the past decade. In light of this, OSHA has determined that additional information concerning hydraulic fracturing and flowback operations hazards should be provided to educate and protect workers. This publication informs employers and workers about the known hazards that result from hydraulic fracturing and flowback and identifies ways to reduce exposure to these hazards. It does not include a detailed discussion of the silica hazards workers potentially experience during hydraulic fracturing operations.