Abstract In Compost-Bedded Pack Barn (CBP) systems, air velocity is linked with the thermal comfort of housed dairy cattle and bedding quality and, therefore, assessing ventilation efficiency is essential. In this context, the objective of this study was to evaluate and characterize dependence and spatial distribution of air velocity at the 1.5 m height (vair,M) and at bedding level (vair,B) in an open CBP system with positive pressure ventilation. The study was conducted in 2021, in a facility located in the Zona da Mata region, Minas Gerais, Brazil. The facility area was divided into a mesh composed of 55 equidistant points, where vair,M and vair,B data were collected in the morning (09:00 a.m.) and afternoon (03:00 p.m.) periods, during three weeks in Brazilian winter. Geostatistics techniques were used to assess dependence and spatial distribution. In both periods evaluated, there were a strong occurrence of spatial dependence and non-uniform vair,M and vair,B distributions. The vair,M and vair,B values were lower than recommended (1.8 m∙s–1) in more than 65.0% of the area. Adequate ventilation levels were observed only in the first 20.0 m of the facility, from Southeast to Northwest, because of the fan lines present.

ABSTRACT This study aimed to characterize the performance of three electrochemical ammonia sensor modules (MQ137, FECS44-100, and MIX2801) in comparison to standard equipment (iPMU) under atmospheric conditions of an open Compost Barn (CB) during the winter period in Brazil. The study was conducted in Cajuri (MG) over three days, collecting data from 06 am to 05 pm on ammonia concentration, temperature, relative humidity, and air velocity in the CB, specifically at the center of the bedding area. The evaluation period was divided into three parts: Period 1 (06 to 09 am); Period 2 (10 am to 01 pm); and Period 3 (02 pm to 05 pm). Recorded data were analyzed using descriptive statistics. It was observed that the greatest discrepancy among the readings occurred in Period 1 (for all sensor modules and the iPMU), due to air saturation conditions. In Periods 2 and 3, readings from the sensor modules closely matched those recorded by the iPMU. Throughout all periods, the MIX2801 showed the most significant discrepancies compared to the iPMU, whereas the MQ137 was the closest to the standard equipment. This finding suggests that the MQ137 is a viable option for use in CB facilities.