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At least 19 recordsLinked to original sources
PubMedDate not supplied

Interaction between air movements and the dispersion of contaminants: clean zones with unidirectional air flow.

The purpose of this presentation is to describe the theoretical relations for the dispersal of airborne contaminants and to illustrate the validity of these equations occurring during factual situations, where a number of observations on air movements in open unidirectional air flow units supplied with HEPA-filters are described. In factual situations the aerodynamic system which governs the dispersion of contaminants in reality is always very complicated that risk situations must be mapped and assessed empirically. The presence of a person can give risk to wakes that may be stable or unstable. The unstable situations are in most cases caused by the influence of arms and hands. As part of the microbiological assessment of aseptic processes carried out in clean zones, it is important to investigate that such vortices do not occur in the clean working areas. As the level of airborne contaminants in the operational environment may have an effect on the level of product contamination, the microbiological assessment of aseptic processes is important. A system is described for microbiological assessment in unidirectional air flow units by using visual illustrative methods and particle challenge tests (measured by particle counter) for the dispersion and/or induction of particles.

Air Microbiology↗
PubMed1984

The effect of air movement on the activity, lying position and huddling behaviour of weaned piglets.

An experiment was carried out in a 55-sow, specific pathogen-free commercial unit, to observe the behavioural adaptation of newly weaned pigs (7 to 10 kg) to air movement in a typical weaner pen. Direct air currents were generated by a fan placed at 4 positions around the pen. Observations were made of activity, lying position, huddling and orientation. Increased activity was observed when the wind was directed on to the preferred lying area of the pigs. The pigs usually moved out of the region of greatest air movement and indirect currents appeared to be more favourable. Wind inhibited huddling in the pigs when it was directed over the lying area but orientation was unaffected. Social factors were important in the choice of lying position. The percentage of pigs huddling gave a behavioural indication of the suitability of the husbandry environment for production and welfare.

Air Movements↗
PubMed1977

[Air movements and animal performance in temperatures above the optimum].

High indoor temperatures in modern stables of livestock farming units have to be offset to avoid loss in animal performance, and this is possible only through improved heat emission of the organism. Increase in air movement, for the time being, is the most effective method. A theoretical account is given of the amount of air movement required in temperatures above optimum and compared with literature data.

Air Movements↗
PubMed1991

The effect of different levels of relative humidity and air movement on litter conditions, ammonia levels, growth, and carcass quality for broiler chickens.

An experiment using 4,800 commercial broiler males (Ross x Ross) was conducted in 12 climatic chambers. Three levels of relative humidity (RH) (45, 40, to 80, and 75%) and two levels of internal air circulation (7.7 to 9.9 and 17.8 to 24.5 cm/s), with each level replicated and, therefore, forming a 3 x 2 x 2 factorial arrangement of treatments, arrangement of treatments, were imposed as the main effects. Broilers were group weighed and feed efficiencies calculated at 14, 28, and 42 days of age. Percentage dry matter of the litter and a subjective evaluation of general litter conditions (moisture and caking) were scored weekly, with the percentage nitrogen and total quality of litter produced in each chamber measured at the conclusion of the study. Ammonia levels were measured in each chamber every second day. A sample of birds (36) from each chamber was processed at 42 days and scored for litter spots and ammonia burns on the breast and for the incidence and severity of twisted legs, crooked toes, and infected and calloused hocks and foot pads. Mean body weight was significantly greater (32 g) at 42 days of age in birds exposed to 45% RH compared with the two higher regimens of RH. Both the incidence and severity of ammonia burns on the breast and infected foot pads were significantly higher with 75 versus 45% RH. Increases in RH significantly increased caking and litter moisture and reduced the percentage of dry matter and the percentage of nitrogen found in the litter. Ammonia levels were more variable but generally increased with increases in RH. The two levels of air movement within the chambers produced less influence on the environment than RH, although the scores for both litter moisture and caking were significantly lower with increased levels of internal air circulation.

Air Movements↗
PubMed1975

Determination of air movement in stored grain as a factor in dynamic dispersion and distribution patterns of gaseous pesticides (fumigants).

The new research reported herein was motivated by variations in distribution-persistence patterns of fumigant residues (BERCK, 1974). The current developmental program is still underway. In the meantime, measurement of picoliter amounts of SF6 in air by GC equipped with a Ni63 EC detector has been proven useful over an airflow range of 10(-4) to 50 mph, representing a factor of 500,000 in differences in air velocity. Diverse applications have been outlined herein. This is the first case on record where measurement of unassisted airflow in the interstitial air of stored grain has been successfully executed, and which enabled determination of airflow speeds in the range of 0.5 to 7.5 times 10(-4) mph (=3 to 45 inches per hour).

Air Movements↗
PubMed1987

Effect of air movement on operant heat demand of chicks.

Chicks, 8 days of age, were housed in a wind tunnel at temperatures from 12 to 28 C in increments of 4 C. The tunnel was equipped with a microswitch, an infrared bulb located above the switch, and a small electric fan controlled by a rheostat. Following learning, chicks were exposed at each temperature to air speeds of 0, .5, 1.0, and 1.5 m/s according to a Latin-square design. Chicks readily responded to air speed and temperature changes. For each increase of .1 m/s the effective environmental temperature dropped .6 C.

Air Movements↗
PubMed1994

Influence of air movement, facemask design and exercise on upper airway, transpulmonary, and transdiaphragmatic pressures in thoroughbred horses.

The influences of facial airflow, exercise and wearing a facemask on gas exchange and upper airway (Pu), transpulmonary (PTP) and transdiaphragmatic (PTD) pressures were investigated in 6 horses performing an incremental exercise test on an inclined (10%) treadmill. The test consisted of a 2 min walk followed by two 2 min exercise bouts at intensities which produced 40% and 80% of maximal oxygen consumption. Horses performed the test 4 times, once for each of 4 protocols, which involved not wearing a facemask (A), wearing a mask with either no biased flow through it (B), with an expiratory bias of 6300 L/min through it (C), or with an inspiratory bias of the same magnitude (D). Although no statistically significant differences in arterial blood gases, Pu, PTP, or PTD could be attributed to the various protocols, trends that may have been physiologically important were detected. Hypoxemia and hypercapnia associated with exercise were most marked with protocol B and least severe with protocols A or D. PTP was lowest for all tests with protocol D. Of the 3 conditions that required the wearing of a mask, protocol D was associated with the lowest Pu. While impelling air into the respiratory tract, as presumedly occurs with horses exercising over ground, may enhance respiratory function during exercise, this preliminary study does not clearly demonstrate this. Because this is an important consideration when conducting studies involving horses on treadmills, further investigations at higher exercise intensities and with additional methodologies are needed to clarify the issue.

Acid-Base Equilibrium↗
PubMed1980

Air movement and heat loss from sheep. I. Boundary layer insulation of a model sheep, with and without fleece.

A model sheep, made from metal cylinders and hemispheres, was heated electrically. Heat loss by forced convection in a wind tunnel was analysed in terms of the dependence of the Nusselt number (Nu) on Reynolds number (Re). For a bare trunk Nu = 0.095 Re0.684, but with fleece covering the trunk to a depth of 3.5 cm, Nu = 0.0112 Re0.875 when the mean radiative temperature of the the coat was taken as the surface temperature. Heat transfer by convection from the whole body, including legs, was described by Nu = 0.029 Re0.80. However, a bulk Nesselt number should not be used to estimate heat loss from a live sheep in a hot environment if the windspeed is below about 4 m s-1 because the relation between mean surface temperature, Nusselt number and convective heat flux is not unique.

Air Movements↗
PubMed1980

Air movement and heat loss from sheep. II. Thermal insulation of fleece in wind.

Penetration of an animal's coat by wind reduces its thermal insulation and increases heat loss to the environment. From studies of the sensible heat loss from a life-sized model sheep covered with fleece, the average fleece resistance -rf(s cm-1) was related to windspeed u (m s-1) by 1/-rf(u) = 1/-rf(0)+cu, where c is a dimensionless constant. As c is expected to be inversely proportional to coat depth l, the more general relation -k(u) = -k(0)+c'u was evaluated, where -k = l/-rf is the thermal diffusivity (cm2 s-1) of the fleece and c' = cl is another constant (cm). The orientation of the model to the wind had little effect on the bulk resistance of the fleece, but the resistance on the windward side was substantially lower than on the leeward side.

Air Movements↗