Last summer Swedish researchers made various measurements of the indoor air on a tanker powered by LNG. The results are still being analysed, but interviews with the crew and the preliminary test results indicate that the work environment may be better than on ships using traditional fuel oil.
From previous research projects it is a known fact that the fuel used affects the quality of the indoor air in the whole ship. Small leaks, air coming from heaters, separators and other equipment, as well as exhaust fumes from the chimney being sucked into the ventilation system, all contribute to soot, small particles and other gaseous emissions being spread to cabins, mess rooms and the bridge.
Like a fingerprint
“The composition of hydrocarbons in the fuel is like a fingerprint. Samples taken tell us that what is in the fuel tanks also finds its way to the rest of the ship,” says researcher Cecilia Österman at Linnaeus University in Kalmar, who has carried out several measurement studies on board together with Sarka Langer from the IVL Swedish Environmental Research Institute.
In July the research team was aboard an LNG powered tanker to monitor the indoor air. The samples are still being analysed, but Cecilia Österman explains that the first preliminary results indicate that there were no increased levels of methane (LNG is 90% methane) on board above background levels. Had the gas spread around the ship it would have been seen in the measurements.
“No, so far we have not been able to detect any methane residues,” she says. “The general impression of the ship was that it was very clean and fresh, and even smelled good. The crew also feel that the work environment is much better than on other ships.”
Measurements were made over one week with ten fixed measuring stations, including those in the control room and engine room, the day room, the mess and the bridge. Ten people from the crew were also given personal measuring equipment to check the air around them. All categories of personnel were represented in the investigation.
Chefs and engine room personnel
“We know that people working in the engine rooms have the highest exposure to hazardous substances, followed by deck and service personnel. The one exception is chefs, who sometimes have a slightly higher level of hydrocarbons after they have spent the whole day flipping burgers on the griddle. “Overall, the crew is more exposed to hazardous substances than the officers, and that goes for all departments,” says Cecilia Österman.
LNG is not the only alternative fuel used in shipping and other new propulsion systems are becoming more common. Österman and Langer have been making measurements on a number of ships since 2013 to examine the changes to indoor air with different propulsion systems. One example was a ferry that replaced its marine diesel engines with electric batteries.
“The indoor air quality went from good to better, but the difference was not huge,” says Cecilia Österman. “Had they changed from heavy oil to batteries the improvement would probably have been more noticeable. Other measurements we have made show that heavy oil results in the worst indoor air.”
Low levels of toxins
The levels of harmful substances in the indoor air on Swedish ships are far below the limits imposed by the Work Environment Authority. On the other hand, as Cecilia Österman points out, these limits are not so much based on health issues as on political decisions and economic considerations. According to the World Health Organization (WHO), there are no safe levels of exposure to certain harmful substances including the known carcinogens, benzene and benzo(a)pyrene.
“That’s why we should always try to reduce exposure by different means,” says Cecilia Österman. “If you can’t change the fuel it is possible to encapsulate the internal combustion engines, improve ventilation, check over the personal protective equipment or reorganize work so that the same person is not constantly exposed to bad air.”
Results from this summer’s measurements on the LNG tanker are expected to be finalised during the autumn.
Linda Sundgren, text and photo