Radio frequency identification (RFID) technology uses tags about the size of a postage stamp that assign a unique identification code to any item they are installed in, which a scanner can then read using radio signals. These tags are commonly used to track customers in stores, and are used in certain ID cards and contact-free charge cards. Since these tags, in theory, can be read by any RFID scanner at any time, significant privacy concerns exist, especially if they encode ID information. Thankfully, RFID signals are not hard to block.
Wrap the object containing an RFID chip in aluminium foil. This blocks the signals from reaching it. If you are worried about people covertly reading ID information, line your wallet with a layer of foil to block signals from the RFID chip in your identification card.
Put any object containing an RFID chip inside a container made of metal or any other conductive material. This shields them from radio signals, including the ones from an RFID scanner.
Surround any object that has an RFID tag with water. RFID signals do not easily penetrate liquids. Placing a RFID chip in a tank of water, or just surrounding it with bottles containing liquid, conceals it from scanners.
Block the signals at their source. If you know where an RFID scanner is located, surrounding it with liquid, aluminium foil or a metal container blocks the signals it is trying to send to detect RFID tags. In most situations, this is not practical, as these scanners may either be hidden or numerous enough to make it difficult to block all of them.
Do not interfere with RFID equipment in stores or in RFID tags in products you have not yet bought. In both cases, this constitutes property damage and may result in criminal prosecution. Blocking the signals with a container, though, is not illegal.