The National Fire Protection Association standard 652 (NFPA) defines combustible dust as a finely divided combustible particulate solid that presents a flash fire or explosion hazard when suspended in air over a range of concentrations and requires the evaluation of suspect dust. American Society for Testing Materials International (ASTM) developed test method E1226 (ASTM E1226) to provide a standard test method characterizing the explosibility of particulate solids of combustible materials suspended in air. The Siwek 20 liter apparatus was calibrated with niacin as part of CaRo 15 held by Adolf Kuhner AG. A maximum explosion pressure (Pmax of 8.4 bar was recorded during the calibration which is within the provided reference values of 7.3 to 9.0 bar. Pulverized Pittsburgh Coal is listed as a calibration material within the ASTM E1226 standard. When evaluated within the Siwek 20-L vessel the Pulverized Pittsburgh Coal a Pmax value of 7.7 bar was recorded. The reference value provided for Pulverized Pittsburgh Coal is 7.0 bar. The discrepancy between the recorded and reference value has raised the question how different vessels, energy requirements and testing procedures influence recorded test values for Pulverized Pittsburgh Coal. The research presented herein investigates the explosive characteristic of Pulverized Pittsburgh Coal dust using the latest ASTM E1226-12a test standard and compares the results to the Unites States Bureau of Mines' PRL 20L vessel. Pulverized Pittsburgh Coal dust concentrations, ranging from 30 to 1,500 g/m3, were tested in a Siwek 20 liter apparatus, an ASTM E1226 compliant vessel. The Pulverized Pittsburgh Coal dust is characterized by maximum explosion pressure (Pmax), the maximum rate of pressure rise (dP/dt) max, and explosibility index (Kst-max). The data presented in this paper vary from the USBM data with a higher Pmax and Kst. The data variances are indicative of the impact of the different testing apparatus and procedures.