2 farmworkers killed in South Dakota silo accident

Two workers have died after being trapped inside a farm silo on a South Dakota operation. 

The incident occurred Saturday on a farm near Volga. The Brookings County Sheriff’s Office said in a Facebook post that the individuals died while repairing the roof of an 80-foot Harvestore silo.

The sheriff’s office and local emergency services responded to the incident at approximately 11:25 a.m. Despite rescue efforts, both workers were pronounced dead at the scene after becoming trapped inside the nearly full silo.

The individuals, identified as Larry Dalzell, 51, of Murfreesboro, Tennessee, and Randi Vandekieft, 41, of Warner Robins, Georgia, were employees of Heartland Tank Inc. The sheriff’s office said it believes they were overtaken by toxic gas, commonly referred to as “silo gas,” during their work. The specific circumstances leading to their entrapment remain under investigation.

Silo gas, primarily nitrogen dioxide (NO2), is a byproduct of forage fermentation inside silos. The gas, which can be extremely toxic, forms in silos as crops decompose. While its concentration peaks two to four days after filling the silo, it can linger if the silo is not properly vented, posing a significant risk to individuals who enter. Even in low concentrations, the gas can be hazardous, with a bleach-like odor often mistaken for smoke from a fire.

The silo involved in the accident uses a top unloading system, meaning workers sometimes need to enter the structure to adjust the machinery as the silage level lowers, increasing the danger of exposure to toxic gases.

Experts recommend waiting at least three weeks after filling a silo before entering and running a blower to ventilate the area for up to 45 minutes before and during entry. Workers are also urged to use proper protective equipment, such as self-contained breathing apparatuses, and never to work alone when entering a silo.

The Brookings County Sheriff’s Office said it is continuing to investigate the incident.