There is a simple and visual way, based on the qualitative reaction of mercury with iodide of copper. The formed substance with the formula Cu2(HgI4) has a pink-red color. The higher the concentration of mercuryis, consequently, more intense coloring it.
To produce the indicator, you will need a porous filter paper, any soluble salt of copper, for example, chloride, sulfate, a salt solution of potassium iodide or sodium iodide, and a solution of sulphite or hyposulphite of sodium.
Paper cut into strips (size is unimportant, but smaller is better), dipped in solution of salt of copper, after which it is removed, slightly dried, and dipped in solution of salt of iodine. The copper iodide formed will be mainly in the pores of the filter paper and iodine on the surface for his paper "boburiy". Then the strips are placed in a solution of sulfite (hyposulphite) of sodium. Iodine is removed (this is evident by the discoloration of the paper). The strips should be washed in clean water, dry. They're ready. It is advisable to store them in a dark place, in closed containers.
If there is a suspicion that in the air there are pairs of mercury, it is necessary to put one strip in each check area. After a few hours, check for any changes. If it was pinkish-red is alarm. So, there is in the air mercury! It is necessary to take measures for detection and removal of the source of this poison.