FAIMS and DMS operate on the same principle: sample molecules in the gas phase are ionized and the resulting ions pass through a drift region to which a high-frequency waveform is applied. Identification of compounds is achieved by measuring the difference in ion mobility at high electric field relative to low field. This technique is similar to ion mobility spectrometry (IMS), with the exception that a high-frequency waveform is not applied in IMS. Advantages of FAIMS/DMS over IMS include higher sensitivity, better selectivity, and reduced size.