Testing av ventilasjonssystem på diverse overbygde standplasser

As a part of the measures to prevent exposure to fumes the Norwegian Defence has decided to install ventilation systems on covered firing points. The Defence Estate has commissioned FFI to test several finished installations of the system at Rena, Terningmoen, Råvatn, Frigården and Sessvollmoen. These represent three different categories of covered firing points; “open point of firing”, “closed point of firing” and “point of firing with noise-deflected walls”. To look at improvement in fume concentration, carbon monoxide (CO) was used as an indicator. CO was measured using detectors mounted on the shoulder on a varying number of gunners. At two ranges (Frigården and Råvatn) metal dust in the gunners breathing zone was also analyzed. Particulate matter was collected using a particle with an airflow of 2 l/min through the filter. The filters were microwave digested (UltraWave) and analyzed for metals (ICP-MS) at the laboratory. The gunners fired several series of 69-100 shots using different configurations of the ventilation system. All tests were performed with HK416. On “open point of firing”-ranges the ventilation systems had variable effect, both no effect (Rena, lane 3) and good effect (Sessvollmoen, lane 15). Side ventilation was installed on Rena, lane 3, which intended to reduce the fumes that have a tendency to accumulate in this zone. The side ventilation did not seem to reduce the concentration of fumes significantly in this zone. The fume concentration was initially low on the “open points of firing” due to natural ventilation. At the “closed point of firing”-lane 17 at Sessvollmoen, the ventilation system had a moderate effect on the reduction of the CO concentration. FFI recommends that ventilation systems are installed on all covered firing points that are “closed” and “open”, prioritizing “closed” lanes. Covered firing points on Råvatn and Frigården is equipped with noise barriers. The covered firing points with noise cancelling have a layout that makes the fumes accumulate around the gunner. The ventilation system on Frigården is based on two diffuser units. One behind the shooters that blows the gun smoke ahead of the shooters, and one that blows the fumes through the noise-cancelling addition in front and out in the open. The first ventilation system that was installed on Råvatn did not have an effect, and did not reduce the fume concentration around the shooter adequately. A new ventilation system was later installed on Råvatn, this was based on a diffuser unit behind the shooter that is to blow the fumes ahead of the shooter, and two vent units in front to remove the fumes from the addition. No effect was observed from the new ventilation system. It is recommended that new solutions are developed for these kinds of covered firing points with noise cancelling, including reconstruction of the covered firing points.