Operators involved in drilling in the offshore petroleum industry are exposed to drilling mud. Personal exposure to oil mist and oil vapour decreased from the period 1985-97 to the period 1998-2009, but in the latter period the limit values were still exceeded in several measurement series. Since 2009, measurement data have not been collected and compiled systematically, and current exposure levels are therefore uncertain. New assessment practice for comparing the measurement results with the limit values (NS-EN 689) is likely to lead to stricter exposure assessments.


The objective was to assess exposure measurements for oil vapour and oil mist, as well as to investigate the exposure of drilling deck workers and factors that influence the measurement level. Further objectives were to assess new practices for comparing measurement results with the limit values, evaluate the quality of the measurement reports, and describe areas with improvement potential.


The project results show that exposure to oil mist among drilling deck workers was lower in 2012-2020 than in 1998-2009, but there was no change for oil vapour. There was higher exposure on mobile than on fixed installations. More recent installations (built from 2018 to 2020) are primarily mobile. Many factors have been shown to contribute to reduced exposure, including lower mudflow, lower viscosity base oils, enclosed shakers, and various combinations of technical measures. In 2018-2020, the median and average for oil mist and oil vapour were lower than the limit values. Under new assessment criteria, 41% of all measurement series would have resulted in direct requirements for measures. Based on former criteria in the Norwegian Labour Inspection Authority's 450, 10% of all measurement series (all concerning oil vapour) resulted in requirements for measures. The measurement reports were generally of good to very good quality, but a few were weak.

Potential for improvement

The project has proposed the following improvement potentials:

  • A sampling strategy/exposure assessment should be established to provide a better estimate for full-shift exposure.
  • Best practice should be discussed in the industry.
  • Developing the measurement method for oil mist and oil vapour with a sampling time up to a full shift’s length will enable measurements that cover full shifts. Exposure assessment for other hazardous components of drilling mud, especially benzene, will be required in an overall risk assessment.
  • When establishing new measures, such as new shaker technology, exposure measurements should be carried out in a systematic way to investigate the extent to which this contributes to reducing exposure.