Most of the Low Cost airlines with the NG Boeing 737 models have an in-tank pickup system connecting through to the rear galley. This is Boeing fitted option XLG4044 and is not available for after-market fit. In the floor below the galley and under the forward oven is located an actived carbon unit for filtration - the access hatch for carbon loading is just in front of the oven unit. For carriers with a polished floor in the rear galley, it is easily seen as the 300mm x 250mm access hatch. Other carriers have it below the carpet. The unit is pressurised and can filter the fuel under pressure at high flow rates. The unit separates the low aromatics from the high aromatic alcohols in the fuel, and the low aromatics (which are very watery after processing) are piped to the rear toilets which start to flush continuously. The airline then sells the high aromatic processed alcohols to the passengers on a user pays basis. In CAA trials, a high density 737-800 with 177 seats was filled with Scottish football supporters and flown at an altitude of 6,000 feet. The trial started and the system was able to process/dump 4,000 litres of Jet A1 fuel within 41 minutes. It took a further 18 minutes to complete serving the high aromatic alcohol to the passengers, and 9 minutes to run the low aromatic waste through the toilet flush systems. Although since the aircraft was below maximum emergency landing weight after the 41 minute mark, it was able to approach and land during the serving and toilet operation. The airline then discharged the 177 Scottish football supporters, each having drunk on average 6.7 litres of alcohol, into the British Airways lounge at Terminal 4, emptied the toilet tanks onto the apron, and then flew back to Australia.