• ARID’s PERMEATOR System Earns CARB Certification...
• PERMEATOR Systems to be Installed at ALL H-E-B Houston area sites...
• ARID Receives Certification from Maryland...
• Independent 3rd Party Field Testing Confirms...
• Texas ORVR Certification Approval...
• ARID Announces Completion of Study...
• ARID announces appointment...
• Vapor Recovery Around the World
• Retooling the Vapor Recovery System
• Membranes, Molecules and the Science of Permeation

• No ORVR and no Stage II (uncontrolled stations). In this scenario, refueling will contribute to significant liquid evaporation as atmospheric air is ingested into the storage tank via the vapor vent or breaches in the vapor piping. The air will enter at a volume equivalent to the volume of liquid dispensed, and upon re-equilibration, this air will generate significant emissions.
• Stage II only (no ORVR). In this scenario, atmospheric air and hydrocarbon vapors enter the storage tank when gasoline is pumped to the automobile. Some typical vacuum-assisted systems obtain high collection efficiencies at the expense of introducing excess air into storage tanks. For example, if 10 gallons of liquid gasoline are pumped to an automobile, the vapor volume returned to the storage tanks may range from 11 to 25 gallons. This excess air/vapor volume will quickly increase storage tank pressure.
• ORVR only (No Stage II). While the ORVR system may capture the refueling vapors as designed, atmospheric air will enter the storage tank as described in the first scenario above (uncontrolled stations).
• ORVR and Stage II. As the ORVR system captures vapors displaced from the automobile fuel tank, the storage tanks will be back-filled with atmospheric air.

Where vacuum-assisted Stage II systems are employed, the storage tanks will be backfilled with atmospheric air at a volume greater than the volume of liquid dispensed. In these cases, the combination of excess gaseous volume and extremely low hydrocarbon concentration will result in rapid storage tank pressurization and subsequent emissions.

These emissions come through either the vent pipes (vent emissions) or leaks in the vapor piping (fugitive emissions). If the vacuum-assisted systems are disabled during refueling of ORVR-equipped vehicles, the resulting storage tank evaporative losses will be equivalent to those generated at uncontrolled dispensing facilities. This must be the case, since the air ingestion volume will be equal to the volume of liquid dispensed.

If balance Stage II systems are used, the storage tank evaporative losses will be equivalent to those generated at uncontrolled stations. This, again, is because the air ingestion volume will equal the volume of liquid dispensed.

In summary, no matter what the scenario, the space vacated by pumping gasoline out of the storage tank is replaced by air or hydrocarbons that are equivalent at least to the volume of liquid displaced. In some cases involving Stage II systems and ORVR, the volume of air ingested is greater than the volume of liquid displaced.