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An assessment of gases in oxygen-deficient hay silos and the effects of forced ventilation.

Kedan G; Spielholz P; Sjostrom T; Trenary B; Clark RE
J Agric Saf Health 2007 Feb; 13(1):83-95
Many modern tower silos used in the agricultural industry for hay and grain storage are oxygen-limiting by design. Forced-air ventilation using a forage blower is a method commonly used to decrease concentrations of toxic and asphyxiant gases and to increase the O2 content within a silo headspace prior to worker entry. This article describes the methods used to measure gas concentrations and the results obtained from a pilot study by the Washington Fatality Assessment and Control Evaluation (FACE) program of two oxygen-limiting forage tower silos in eastern Washington State. The silos were monitored for oxygen (O2), nitrogen dioxide (NO2), and carbon dioxide (CO2). Measured O2 concentrations were low in all areas of the headspaces monitored for both silos. After beginning forced-air ventilation, O2 concentrations within the silo headspace returned to ambient levels within 8 to 20 min. Nitrogen dioxide levels exceeded the Washington Industrial Safety and Health Act (WISHA) short-term exposure limit (STEL) in the silo that was filled six days earlier (silo 2), but not in the silo that was filled four days earlier (silo 1). The NO2 concentration in silo 2 decreased to below the WISHA STEL within 15 min of starting ventilation but began to rise shortly after ventilation was stopped. Carbon dioxide, which was only measured in silo 1, was detected at 2% within the headspace of this silo. The carbon dioxide concentration decreased to <1% within 3 min of starting ventilation.
Farmers; Agriculture; Agricultural-workers; Agricultural-industry; Sampling; Gas-sampling; Gases; Ventilation-equipment; Ventilation; Confined-spaces; Author Keywords: Gases; Measurement; Silos; Ventilation
Publication Date
Document Type
Journal Article
Funding Type
Cooperative Agreement
Fiscal Year
Identifying No.
Cooperative-Agreement-Number-U60-OH-008336; Cooperative-Agreement-Number-U60-OH-008487
Issue of Publication
Source Name
Journal of Agricultural Safety and Health
Performing Organization
Washington State Department of Labor and Industries
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division