In much of the U.S., the drop in temperature which signals an approaching winter means that farmers and farm workers will be throwing on a heavier jacket and perhaps think about digging out a warmer hat and gloves. Unfortunately, cooler weather also will lead to an increased threat of carbon monoxide poisoning. The cooler weather encourages us to close-up buildings and fire-up the heaters to create a comfortable working environment. It makes us want to fire-up space heaters at home. The blowing wind and snow makes it inconvenient and uncomfortable to work outside.  

In the U.S., between the years 1999 and 2004, over 16,000 death certificates listed carbon monoxide (CO) poisoning as a contributing factor or cause. More than 15,000 hospital visits occur each year as a result of unintentional exposure to carbon monoxide. Carbon monoxide is an odorless, colorless gas which is a byproduct of incomplete combustion. It is produced by fuel burning equipment and appliances such as engines, combustion-based heaters, furnaces and wood stoves. If they are not properly ventilated or are operating inappropriately, CO can build up in an enclosed space creating increasingly higher concentrations of CO. Inhalation of CO results in a reduction of the blood’s ability to transport oxygen through the body. People experiencing low level CO poisoning report flu-like symptoms including: dizziness, nausea, headache, lethargy and weakness. At higher concentrations symptoms can also include confusion, fainting, impaired vision and/or hearing. Extended exposure can lead to unconsciousness and death.

Research reported in Michigan from 2010 indicated that the two greatest causes of unintentional CO exposure in the workplace were furnace/water heaters and power equipment. Some of the greatest contributors to unintended CO exposure in the home were reported as from vehicles, furnace/water heaters, fire, generators, wood stoves and portable heaters. There was also a sizable contribution from “Other” for both groups. 

A two-pronged strategy is required to prevent and protect against the risk of carbon monoxide poisoning. First, be aware of and have a plan to identify and pre-empt or avoid potentially risky situations where carbon monoxide could collect. In buildings with gas heaters, furnaces, wood stoves, or even water heaters, ensure there is adequate ventilation and ensure they are installed and maintained by professionals following local installation codes. A commonly used ventilation standard is 1 square inch of fresh air per 1000 BTU of heating capacity.  These carbon monoxide producing appliances should be inspected annually. Farms supplying employee housing should work with the occupants to ensure stoves and charcoal grills are not being used as a supplemental heat source. The operation or use of internal combustion engines in generators, lawnmowers, snow blowers, automobiles and power-washers in enclosed spaces should be prohibited. Develop and implement a safety SOP which requires an open door or ventilation point when operating combustion engines on the farm.

Secondarily, though no less important, the installation of carbon monoxide detectors will assist in the prevention of unintentional CO exposure. These units should be installed in sleeping rooms in farm dwellings and in enclosed work spaces on the farm where potential exposure to the exhaust from gas-fired heaters, water heaters and internal combustion engines may collect. Following the manufacturer’s installation instructions and maintenance recommendations will maximize the effectiveness of the detectors. Most manufacturers call for replacement of batteries twice each year. Detectors should also be replaced after several years because the sensitivity of the detector unit degrades over time as dust and other contaminants build up on its surface (Smoke detectors should also be replaced every few years as well.). 

Dean Ross is an agrosecurity and dairy farm management consultant based in Michigan.  He can be reached at