My main objection to these machines is that they use the wrong technique, and therefore, will not be effective at the job at hand. All scientists know that you should always use appropriate methodology, or you will get bad results, risking not finding what you are looking for and uncovering a whole bunch of stuff you won´t know what to do with. If you want to detect explosives, you should look for a specific set of chemicals that can be explosive, not check for any form of object just above people´s skin.