A portable minianalyzer was built for mercury determination in air which is based on cold vapor atomic absorption spectrometry (CVAAS) at 184.9 nm mercury line. The new instrument was made of the following principal units: a low pressure mercury lamp, a flow cell, a radiation detector (a special photomultiplier tube, sensitive only to radiations of λ < 200 nm), an electronic amplifying and displaying system and a line for analyzed air and mercury vapor standards circulating through the minianalyzer. The developed mercury minianalyzer is a non-dispersive instrument (without monochromator, lens or other optical components). The mercury vapors in air could be determined between 0.25 and 20 μg Hg/m3. Its sensitivity for mercury vapor determination at 184.9 nm line was 2.54 times higher in comparison to measurements done at 253.7 nm line with a commercially available instrument. It's cheaper, simpler and more sensitive than the commercially available mercury vapors minianalyzers.