Background: The Swedish nuclear power plant Forsmarks Kraftgrupp AB (FKA) reported that they wanted to use a fi re prevention method by reducing the oxygen level down to 15% in some locations. The personnel are only going to work there for a limited number of hours. This fire protection method has never been used before in any nuclear power plant in spaces where people work. The background to the study was the lack of comparable, sufficiently relevant scientific literature on the topic of whether cognitive ability deteriorates or not when the oxygen (O2) level is reduced from the normal level (21%) to 15%, without habituation. SSM needed more knowledge of whether the cognitive abilities of the personnel could be affected in a negative way. The goal of the study was to provide SSM with the basis for oversight.

Objectives: The study was divided into two parts, a literature study and an experimental part. The phenomenon studied was comparable to the situation at the nuclear power plant. The persons involved in the experimental phase were exposed to a change from normal oxygen level to a reduced oxygen level without having time to adapt. The exposure to 15% oxygen was 2 h during the first exposure, 2 h during the second exposure and 45 min during the third and final exposure.

Results: The literature review primarily identified evidence that the effects on cognitive performance due to hypoxia at 15% O2, if any, would be small. A few researchers have reported findings that support adverse effects on cognitive performance already at 16-15% O2 concentration. In support of the hypothesis that no adverse effects on cognitive performance could be observed under conditions studied, there were no significant decreases in cognitive performance as a result of exposure to the experimental conditions with 15% O2. This study was clearly delineated and several possible influencing aspects were not included. Therefore, we cannot rule out possible interaction effects, with negative impact on cognitive ability, between hypoxia and other factors such as diseases, medication and drugs, concussion history, or other aspects of air quality.

Need for further research: There are several aspects of this research that should be of interest for further research by the nuclear industry.

Summary Points:

  • There were no statistically significant differences in performance on the K-D test across baseline (normal room air) and the three exposures to the experimental condition (nitrogen-balanced breathing gas mixture of 15% O2).
  • K-D test results across the total of 16 test occasions showed the largest performance change occurring between the first and second test occasion.
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