| 摘要 |
<p>An apparatus (10) is provided which passively removes contaminated gases form a subsurface (16). The apparatus (10) includes a riser pipe (12) extending into a subsurface (16) which has an exterior end in fluid communication with a valve (32). When well pressure is greater than atmospheric pressure, the valve (32) opens to release contaminants into the atmosphere, and when well pressure is less than atmospheric pressure, the valve (32) closes to prevent flow of air into the well (18). The valve assembly of the invention comprises a lightweight ball (42) which is lifted from its valve seat (40) with a slight pressure drop between the well (18) and the atmosphere.</p> |
