Ah, hockey.

Ice chips spray as a player skates to a stop and digs for a puck in the corner. A cool breeze wafts over the rink in the wake of opposing players rushing down the ice to stop him.

And then there's the yellowish blanket of nitrogen dioxide, a toxic gas that's an ingredient in smog, hovering over them.

Say what?

Early last year, 31 people got sick after spending time at an unnamed indoor ice arena owned by a private school in New Hampshire.

Health officials said a 19-year-old man showed up at a local hospital emergency room shortly after hockey practice, according to an account in the latest issue of Morbidity and Mortality Weekly Report. He was hacking, short of breath and coughing up blood.

Other players on his team were having similar problems. Same, too, for the guys on another team. Many wound up in the hospital.

The problem? The ventilation system in the arena where they practices was on the fritz. So when workers at the arena spent an hour or so buffing up the ice with a propane-powered resurfacing machine, the exhaust, including nitrogen dioxide, stayed inside.

Nitrogen dioxide is heavier than air and, like smog, it can be trapped near the ice by a warmer layer of air on top.

Players, workers and spectators at the rink noticed a yellow haze over the ice during two separate practices. But the players played on. Almost all of them later got sick.

The arena had a monitor to check the air for carbon monoxide but not nitrogen dioxide. The health officials recommended that an nitrogen oxide monitor to be added and that the ice equipment be tested.

The best way to eliminate the potential problem, the report says, would be to use electric rather than propane-powered equipment.

The brand of ice-resurfacing machine wasn't mentioned. But I asked Frank J. Zamboni & Co. — which pioneered the equipment and makes electric-, propane- and natural gas-powered models — for a comment on the report.

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