An e-liquid cartridge (20) designed to supply e-liquid to an electronic cigarette vaporiser, or personal vaporiser (PV), in which the cartridge includes an air pressure valve (31). In some embodiments, the air pressure valve is designed so that as the fluid level inside the cartridge/reservoir falls, atmospheric pressure enables the air pressure valve (31) to allow air to flow into the cartridge/reservoir and ensure equalisation of the air pressure. The valve may be an air-porous e-liquid impermeable PTFE or PTFE-coated layer or membrane (31) or a mechanical valve, and may be oleophobic and hydrophobic. The air facing side of the membrane may include strands of polypropylene. The cartridge lid (28) may comprise a plenum chamber (30). The membrane may be ultrasonically fused with the lid, which may be HDPE, PETG or COC. Also disclosed in a vaporiser system comprising a PV, a case, a microprocessor, a cartridge and a pump.
