Oil shale is the main natural commodity of Estonia. In the present paper the chemical hazards in the air of the work environment during handling of shale fuel oil are investigated. Research focus: the implementation of the flexible risk assessment model worked out in Tallinn University of Technology for assessment of toxic chemicals, the matrix on the basis of the five-step risk assessment model is presented, where the relationship between the exposure concentration and potential health impairment is given. Research methods and materials: 1) the five-step flexible risk assessment model is used; 2) the measurement methods used in the study comprise: a) the gas chromatography-mass spectrometry (GC-MS) to separate the shale fuel oil; b) Dräger tubes for determination the content of chemicals in the air of the work environment. Results: the relationship between the exposure concentration and potential health impairment is given. The occupational illness stages are developed using statistical data of diagnoses of occupational diseases. Conclusion: according to the proposed model, the exposure to toluene and xylene poses justified risk (risk level II), benzene and phenol unjustified risk (risk level III). Recommendations: without any additional control measures applied, the risk for occupational diseases caused by these chemicals is significant; the personal protective equipment should be provided to the workers.