Photo/Illutration Rescuers search for missing hotel workers at the Takayu Onsen hot spring resort in Fukushima in February. (Provided by Fukushima Broadcasting Co.)

FUKUSHIMA—The recent deaths of three hotel workers in the mountains here underscored the dangers of hydrogen sulfide poisoning among people who manage hot spring sources.

Although onsen guests are protected by Environment Ministry standards on bathroom hydrogen sulfide concentrations and ventilation, there are no specific safety rules for hot spring workers.

“In the absence of administrative regulations, workers manage hot spring sources at their own risk,” Fukushima Mayor Hiroshi Kohata told a news conference after the hotel workers died of hydrogen sulfide gas poisoning in February. “We want to consider what the city can do.”

The three victims were the general manager of Kagetsu Highland Hotel at the Takayu Onsen hot spring resort and two employees. They were found collapsed in a depression created by snow on Feb. 18, according to police and the fire department.

Hydrogen sulfide of 5 parts per million (ppm) or higher concentrations was detected at the site.

The three had left the hotel the previous day to take care of a hot spring source in the mountains.

Hot spring water at Takayu Onsen contains high sulfur concentrations, and the pipes there become clogged unless regularly cleaned.

Government regulations call on workers in general not to enter places containing hydrogen sulfide exceeding 10 ppm “without good reason.”

Separately, health ministry rules require hydrogen sulfide concentrations to be kept at 10 ppm or lower to prevent oxygen starvation during work inside sewerage facilities and ship tanks.

Workers at such sites must carry an oxygen cylinder in places with poor ventilation.

However, the rules do not explicitly apply to hot spring facilities.

Junichi Endo, director of the cooperative association of “ryokan” inns in Takayu Onsen, said hydrogen sulfide levels of 10 ppm are fairly common around hot spring sources.

But he said it would be impractical for onsen workers to carry oxygen cylinders, which are heavy and deplete quickly.

“It will not be worth the cost if we strictly follow the rules,” said Endo, 69, who takes care of a hot spring source.

The cooperative association plans to compile a manual for workers who manage hot spring sources.

According to Kagetsu Highland Hotel, the three workers were carrying hydrogen sulfide measuring instruments but not oxygen cylinders or gas masks.

Those who oversee hot spring sources are known as “yumori,” or guardians of hot spring water.

Kiyoji Takeda, a veteran yumori at the Dake Onsen hot spring resort in Nihonmatsu, Fukushima Prefecture, said caretakers like him literally put their lives on the line in winter.

The 73-year-old travels about 8 kilometers to a hot spring source halfway up Mount Adatarayama once a week to clean water pipes.

Large cavities often form around a hot spring source because the hot water melts the snow. Hydrogen sulfide, which is heavier than air, tends to accumulate inside such cavities in windless weather.

Takeda said he does not wear a gas mask to conserve his strength.

“It is not realistic when work efficiency is taken into account,” he said.

Kagetsu Highland Hotel, which reopened on March 5, said on its website it will look into causes of the accident and review its safety measures.

Police plan to investigate whether professional negligence was involved.

(This article was written by Yukiko Sakamoto and Nobuyuki Takiguchi.)

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