A foul-smelling toxic gas release in northern Santa Barbara County last week irritated area residents and created a health hazard, but did little else.

Oil field employees at the Grayson Oil Lease released hydrogen sulfide gas (H2S) – a highly toxic substance that can be deadly if inhaled in high doses – at the oil field in Sisquoc, about 30 miles north of Buellton, on Nov. 11 and 13.

The Santa Barbara County Fire Dept. was notified of the gas release after area residents complained of a fetid odor. The Air Pollution Control District was notified Nov. 13 by the Fire Protection Services Division that the company was releasing the toxic gas. APCD employees went to the scene and witnessed oil field workers deliberately releasing the gas.

A Hazardous Materials Unit inspector visited the site Friday afternoon to determine that proper permitting had taken place and cited the field for releasing the gas.

The fire department said the situation was stable but monitored it throughout the weekend due to resident concerns.

“There was a concern over the weekend, should there be another release,” SB County Fire Dept. on-call public information officer Jan Berkept said.

There were no gas releases over the weekend.

H2S, a colorless gas, is heavier than air and smells like rotten eggs. It can be detected by its repellant scent until between two to 15 minutes of high-level exposure, when victims lose their sense of smell, making the gas impossible to detect. If enough exposure to high levels of H2S occurs, the victim’s respiratory system becomes paralyzed, causing death. Low-level exposure usually causes eye and mucous membrane irritation. Levels of toxicity in residential areas were not high enough to harm residents but caused considerable annoyance.

People whose jobs put them at risk of H2S exposure are required by law to receive safety training and keep face masks nearby for protection in the event of a gas leak. No injuries to oil field employees were reported in the incident.

H2S is highly flammable and will ignite when exposed to heat, flame or oxidizers. When burned, H2S produces sulfer dioxide(SO2), an even more toxic gas.

H2S is used in the preparation of oil additives. During the recovery and processing of crude oil, H2S can contaminate the atmosphere and cause major health hazards. About 10 million tons of H2S are produced in North America each year for use in manufacturing processes.