MONTEZUMA — A deadly gas that killed five people on a farm south of Briery Branch in early July was Hydrogen Sulfide, and not methane as authorities had previously reported.

Dr. Stephen Phillips of Rockingham Memorial Hospital told members of the Mennonite community on Saturday that the gas had reached toxic levels that paralyzed their sense of smell.

Phillips was among several presenters during a farm safety program west of Dayton offered by the Rockingham County office of the Virginia Cooperative Extension Service. Rockingham County Fire and Rescue personnel and other emergency and farm safety volunteers also participated.

Four members of the Scott Showalter family died, including two children, when they were overcome by gas in a manure pit. A farmhand also died.

The natural reaction, Phillips told the gathering at the Shenandoah Valley Produce Auction, is to help anyone struck down. But going into a confined space where gas could be present is not the way to do it, he said.

A meter reading of the gas at the edge of the pit by rescue workers, Phillips said, was at 700 parts per million.

The amount is well above the 500 parts per million that would have been sufficient to fatally incapacitate someone in a matter of moments.

"Anybody who had gone down there without a complete supply of air for themselves would not have made it back," Phillips said of the manure pit at the Showalter farm.

The Showalters and the farm hand did not know what hit them, Phillips said.

Well before reaching the deadly level, hydrogen sulfide paralyzes the olfactory nerve, which is essential for the sense of smell, he said.

"You won’t know you are breathing it," Phillips said.

Authorities had earlier reported that the gas that killed the five victims was methane.

Rockingham County Sheriff Don Farley said police assumed methane was the cause of death before they received the coroner’s report.

"Most of it was assumptions on our part," he said.

Phillips said that methane is lighter than air and rises, while Hydrogen Sulfide is heavier and sinks.

When a build up of gas is detected, the proper response is to try to ventilate the confined space and call emergency services, said Marshall Funk, Virginia Department of Fire programs instructor. But Funk said adequate preparation, including a back-up crew is needed to make sure no one else is injured.

A farm owner at Elk Creek in Grayson County, Funk said the ventilation could buy some time until rescue personnel arrive.

The farm program, which attracted about 400 people, included a demonstration of a pit rescue using a winch.

A person, with an air supply, is lowered into the pit on a harness. The most often asked question, Funk said, is what takes so long to get to the victim.

"You can’t afford to take a chance on this," he said.

Contact Jeff Mellott at 574-6290 or jmellott@dnronline.com