of power over a long period of time. This makes them ill-suited for powering large vehicles (at least directly), but ideal for smaller vehicles such as forklifts and tuggers and consumer goods such as mobile phones, digital cameras or laptops. Military applications of DMFCs are an emerging application since they have low noise and thermal signatures and no toxic effluent. These applications include power for man-portable tactical equipment, battery chargers, and autonomous power for test and training instrumentation. Units are available with power outputs between 25 watts and 5 kilowatts with durations up to 100 hours between refuelings. Especially for power output up to 0.3 kW the DMFC is suitable. For a power output of more than 0.3 kW the indirect methanol fuel cell presents a higher efficiency and is more cost-efficient. Freezing of the liquid methanol-water mixture in the stack at low ambient temperature can be problematic for the membrane of DMFC (in contrast to indirect methanol fuel cell). Methanol Methanol is a liquid from at atmospheric pressure. The volumetric energy density of methanol is an order of magnitude greater than even highly compressed hydrogen, about two times greater than liquid hydrogen and 2.6 times higher than lithium-ion batteries. The energy density per mass is a tenth of than that of hydrogen, but 10 times higher than that of Lithium-ion batteries. Methanol is slightly toxic and highly flammable. However, the International Civil Aviation Organization's (ICAO) Dangerous Goods Panel (DGP) voted in November 2005 to allow passengers to carry and use micro fuel cells and methanol fuel cartridges when aboard airplanes to power laptop computers and other consumer electronic devices. On September 24, 2007, the US Department of Transportation issued a proposal to allow airline passengers to carry fuel cell cartridges on board. The Department of Transportation issued a final ruling on April 30, 2008, permitting passengers and crew to carry an approved fuel cell with an installed methanol cartridge and up to two additional spare cartridges. It is worth noting that 200 ml maximum methanol cartridge volume allowed in the final ruling is double the 100 ml limit on liquids allowed by the Transportation Security Administration in carry-on bags. Reaction The DMFC relies upon the oxidation of methanol on a catalyst layer to form carbon dioxide. Water is consumed at the anode and produced at the cathode. Protons (H+) are transported across the proton exchange membrane - often made