The most fire dangerous in the chemical industry is connected with the chemical reactors. Chemical reagents leaking from chemical reactor can cause fire or explosion. Therefore, mixers rotating shafts of chemical reactors sealing is an important task. Mechanical seals used for this purpose operate with the leakages that decrease fire and explosion safety. Magnetic fluid seals have absolute leak tightness, low friction torque, no wear, long service life and ease of maintenance. Chemical reactors seals should operate reliably when exposed to corrosive environments, high temperature (up to 400 °C), about 1 mm axial and radial shaft runouts. The results of the research showed that the magnetic nanofluid type F1-20 (based on the organofluorine liquid) is resistant not only to the hexane, chloroform, toluene, acetone, ethyl acetate, but such potent solvents as N,N-dimethylformamide and tetra-hydrofuran. Also, magnetic nanofluid type F1-20 successfully passed the temperature test for 300 hours at 150 °C. To limit the aggressive environment influence on magnetic fluid seal parts the seal with a protective element in the form of a reverse type hydraulic valve has been designed. It is proposed to install magnetic fluid seal in special rubber bushings to compensate shaft runout. Designed special magnetic system allows to isolate the permanent magnet from the aggressive environment. Special magnetic system also permits to regulate magnetic induction in the seal air gap to obtain optimal performances and the magnetic fluid durability. The investigations allowed us to develop new design of magnetic fluid seals for mixers shafts 95 and 110 mm diameter of chemical reactors 6 and 10 m3. Designed seals were made and installed on chemical reactors of paint production company "Lakokraska" (Yaroslavl). Installed magnetic fluid seals eliminated reactants leakages and as a consequence increased fire and explosion safety of the production.