A flame arrestor, comprising: a body having a passage to enable fluid communication between a first end of the passage and a second end of the passage ; and a plug disposed within the passage to substantially fill a cross-sectional area of the passage ; characterized in that : the first end of the passage includes a shoulder , wherein a diameter of the passage is substantially constant from the second end of the passage to the shoulder and decreases from the shoulder toward the first end of the passage ; a first end of the plug engages the shoulder ; the plug is configured to provide a gap between an exterior surface of the plug and a wall of the passage to fluidly couple the first and the second ends of the passage ; and the plug includes at least one slot at the first end of the plug extending along an exterior surface of the first end of the plug , the at least one slot extending across the entire diameter of the first end of the plug between opposing peripheral edges of the first end of the plug to direct fluid flow in the slot toward the wall of the passage and along the gap and the exterior surface of the plug toward the second end of the passage . a body having a passage to enable fluid communication between a first end of the passage and a second end of the passage ; and a plug disposed within the passage to substantially fill a cross-sectional area of the passage ; characterized in that : the first end of the passage includes a shoulder , wherein a diameter of the passage is substantially constant from the second end of the passage to the shoulder and decreases from the shoulder toward the first end of the passage ; a first end of the plug engages the shoulder ; the plug is configured to provide a gap between an exterior surface of the plug and a wall of the passage to fluidly couple the first and the second ends of the passage ; and the plug includes at least one slot at the first end of the plug extending along an exterior surface of the first end of the plug , the at least one slot extending across the entire diameter of the first end of the plug between opposing peripheral edges of the first end of the plug to direct fluid flow in the slot toward the wall of the passage and along the gap and the exterior surface of the plug toward the second end of the passage . the first end of the passage includes a shoulder , wherein a diameter of the passage is substantially constant from the second end of the passage to the shoulder and decreases from the shoulder toward the first end of the passage ; a first end of the plug engages the shoulder ; the plug is configured to provide a gap between an exterior surface of the plug and a wall of the passage to fluidly couple the first and the second ends of the passage ; and the plug includes at least one slot at the first end of the plug extending along an exterior surface of the first end of the plug , the at least one slot extending across the entire diameter of the first end of the plug between opposing peripheral edges of the first end of the plug to direct fluid flow in the slot toward the wall of the passage and along the gap and the exterior surface of the plug toward the second end of the passage . <EOS>