Introduction:
There are various magnetic field sources of unknown induction levels installed in schools. The aim of this research, is to evaluate level of magnetic induction in classrooms and workrooms of chosen schools in Katowice area.

Material and Methods:
Magnetic induction measurements were taken in 10 primary schools, 12 middle schools and 4 secondary schools in Katowice area. Magnetic induction was measured in at least two classrooms i.e. in a computer science classroom and in a humanities subject classroom. Induction level was inspected by means of spot measurement.

Results:
In most schools, which were evaluated, magnetic induction level did not exceed 50 nT. Measurements taken in middle schools and secondary schools showed higher magnetic induction values in computer science classrooms in comparison to humanities subject classrooms. Mainly of year production and technical condition of installed computer equipment influenced magnetic induction level measured in computer science classrooms. Older computers generated higher levels of magnetic induction, in comparison to new equipment. In a part of one primary school, which was 120 years old, in humanities subject classrooms, measured magnetic induction was higher then 150 nT. In another primary school localized in highly industrialized area near coal mine, magnetic induction inspected in computer science classrooms was higher, then 400 nT, whereas induction level in humanities subject classrooms of this school oscillated around 100 nT. The highest levels of magnetic induction were measured in two schools, in which transformers were installed. The measured level of magnetic induction in one of the above mentioned schools was 200 nT.

Conclusions:
Because different magnetic induction levels are strictly related to the computer equipment type, the level of exposure of children and youth to magnetic induction should be evaluated, after installing the equipment.