The incident happened at about 1:15 p.m. in Lytton.

Both men, one of whom had briefly stopped breathing, were taken to Loring Hospital in Sac City. A report on their conditions was not available Monday evening.

A crew from Sargent Drilling, of Carroll, was injecting 110 gallons of hydrochloric acid into the well when a chemical reaction occurred, according to Fort Dodge Fire Chief Steve Hergenreter. He said a large cloud of what was later identified as hydrogen sulfide was created.

A worker in the well building was overcome by the gas, Hergenreter said. One of his co-workers went into the building and pulled him out.

Hergenreter said the worker who was overcome was not breathing when he was pulled from the building. He said Calhoun County 911 dispatchers instructed the second man in performing CPR. As a result, the patient was breathing when emergency personnel arrived.

The Region V Hazardous Materials Response Team operated by the Fort Dodge Fire Department was called to the scene.

Hazardous materials team members in full protective gear identified the gas as hydrogen sulfide. Hergenreter said at that time the amount of gas in the well building was 10 times the level at which it is considered lethal.

The hazardous materials team flushed the acid in the well, eventually dissipating the hydrogen sulfide.

The Lytton Fire Department, Calhoun County Emergency Medical Service, Calhoun County sheriff’s deputies and Calhoun County emergency management responded to the scene along with the hazardous materials team.