Early suppression fast response (ESFR) sprinklers were developed to meet the demands of high challenge storage fire scenarios and are a common choice to protect warehouses. Many aspects of ESFR sprinklers are unique compared to standard spray sprinklers. Paramount to ESFR sprinkler performance is the ability of the sprinkler to provide large amounts of water, in a specific discharge pattern, to the fire source in the incipient phase of fire development. Obstruction of the sprinkler discharge pattern could greatly affect the ability of the ESFR sprinkler to achieve fire suppression. Phase 1 of the Fire Protection Research Foundation's latest project...