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At least 19 recordsLinked to original sources
PubMed2004

Air movement--good or bad?

UNLABELLED: Air movement--good or bad? The question can only be answered by those who are exposed when they are exposed. Human perception of air movement depends on environmental factors including air velocity, air velocity fluctuations, air temperature, and personal factors such as overall thermal sensation and activity level. Even for the same individual, sensitivity to air movement may change from day to day as a result of, e.g., different levels of fatigue. Based on existing literature, the current paper summarizes factors influencing the human perception of air movement and attempts to specify in general terms when air movement is desirable and when it is not. At temperatures up to 22-23 degrees C, at sedentary activity and with occupants feeling neutral or cooler there is a risk of air movement being perceived as unacceptable, even at low velocities. In particular, a cool overall thermal sensation negatively influences the subjective perception of air movement. With occupants feeling warmer than neutral, at temperatures above 23 degrees C or at raised activity levels, humans generally do not feel draught at air velocities typical for indoor environments (up to around 0.4 m/s). In the higher temperature range, very high air velocities up to around 1.6 m/s have been found to be acceptable at air temperatures around 30 degrees C. However, at such high air velocities, the pressure on the skin and the general disturbance induced by the air movement may cause the air movement to be undesirable. PRACTICAL IMPLICATIONS: Based on existing literature, the paper summarizes factors influencing the human perception of air movement and attempts to specify in general terms when air movement is desirable and when it is not.

Air Movements↗
PubMed2004

The effective use of simulated natural air movement in warm environments.

UNLABELLED: Air movement can be characterized by its mean velocity, turbulent intensity, power spectra, velocity distribution probability, etc. Based on a field test, it was found that the characteristic of an artificial air movement is different from that of natural wind. In order to simulate the characteristic of natural wind, two air supply devices were investigated. Furthermore, the acceptability of the subjects exposed to the simulated natural wind is higher than that of subjects exposed to artificial air movement. Through the subjective assessment, the preferred mean air velocities at different ambient and supply air temperatures are presented. Finally, a conditioning mode using fluctuated air movement in warm climates, and a prediction of energy savings are given. PRACTICAL IMPLICATIONS: The paper demonstrates how a simulated natural air movement may improve comfort and save energy in warm climates.

Air Movements↗
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↗
PubMed2003

[Usefulness of monitoring forehead deep-tissue temperature as an index of core temperature in adult patients undergoing laparotomies under general anesthesia--investigation in operating rooms with air-movement control system using vertical flow].

BACKGROUND: Acute changes in air temperature in the vicinity of the patents' forehead may impair clinical usefulness of the forehead deep-tissue thermometry. We thus investigated usefulness of monitoring the forehead deep-tissue temperature as an index of core temperature in 12 adult patients undergoing laparotomies in operating rooms with air-movement control system using vertical flow. METHODS: Nasopharyngeal, forehead deep-tissue, palm deep-tissue, and fingertip skin-surface temperatures were recorded during surgery every 5 minutes in operating rooms where room temperature was thermostatically controlled at approximately 25 degrees C. The patients were not actively warmed with forced-air warmers, but covered with cotton blankets where possible. The deep-tissue and fingertip skin-surface temperatures were compared with the nasopharyngeal temperature using regression and Bland and Altman's analyses. RESULTS: The four temperatures continued decreasing during surgery, and the nasopharyngeal temperature decreased to below 36 degrees C 2 hours after induction of anesthesia. Only the forehead deep-tissue temperature satisfactorily correlated with the nasopharyngeal temperature (r = 0.76, n = 300, P < 0.0001). The difference between nasopharyngeal and forehead temperatures was +0.26 degree C, and its standard deviation was 0.34 degree C. CONCLUSIONS: The forehead deep-tissue temperature has sufficient accuracy and precision for clinical use in operating rooms with air-movement control system using vertical flow. However, the core temperature appears to be slightly underestimated with the forehead deep-tissue thermometry.

Adult↗
PubMedDate not supplied

Air movement visualization in the workplace: current methods and new approaches.

Airflow visualization in the workplace to assess containment, ventilation, or general air movements is often carried out using smoke tracers. The most prevalent method uses a disposable smoke tube that generates a plume of concentrated sulfuric acid fume. However, use of the smoke tube exposes occupational hygienists to the risk of sulfuric acid exposure through inhalation or dermal contact, as well as injury from sharps. Following concern over the potential health hazard associated with smoke tube usage, alternative flow visualization methods and technologies have been reviewed. Methods of generating smoke or bubbles other than using smoke tubes suitable for visualizing air movements include heated element smoke generators, combustion generators, generation of metallic chlorides and ammonium chloride, generation of neutral density bubbles, and water fog generation. Some of these methods are applicable in specific workplace situations. However, there is no commercially available smoke or bubble generator currently available that matches the smoke tube for cost effectiveness, ease of use, and wide applicability, while also reducing the potential health risks associated with smoke tube usage. Despite this, certain technologies, in particular water/glycerol smoke generation using heated element generators, have the potential to be developed into viable alternatives to the smoke tube. Thus, with further development, an air movement visualization method that poses a significantly lower health hazard than the smoke tube is feasible.

Aerosols↗
PubMed2006

Air movement evokes electro-olfactogram oscillations in the olfactory epithelium and modulates olfactory processing in a slug.

In many animals, neurons in the olfactory system have been shown to respond not only to odorants but also to air movements. However, the manner in which the mechanical dynamics of odor stimulation affect olfactory processing remains poorly understood. Using a series of flow rates and odor concentrations from clean air to high-concentration vapors, we systematically analyzed the effects of air movement and odor concentration on olfactory processing. We extracellularly recorded local field potentials and spike units from the olfactory epithelium (OE) and tentacular nerve (TN), which connects the first and second relay centers of olfactory information, in the terrestrial slug Limax marginatus. We found that clean air puffs at a flow rate of 0.18 ml/s (gentle wind), but not high-concentration odor puffs at lower flow rates, induced electro-olfactogram (EOG) oscillations in the OE with a constant frequency (2.5 Hz), regardless of the odor. Surgically isolated OE preparations also showed these EOG oscillations, indicating that the oscillations arose from the OE independently of the downstream circuits. The EOG oscillations entrained the slower spontaneous TN oscillations (1-2 Hz) to the fixed rhythm (2.5 Hz). Spontaneous and odor-evoked units were phase-locked to the TN oscillation peaks. This TN oscillation entrainment by the EOG oscillations caused stronger phase-locking, specifically TN oscillation peaks and EOG oscillation troughs. Taken together, these results suggest that when odors are carried by a gentle wind, the air movement induces EOG oscillations and modulates rhythmic spike patterning of olfactory outputs to the second olfactory relay center in Limax.

Action Potentials↗
PubMed1998

Air movement and the thermal microclimates observed in poultry lairages.

1. The thermal environment experienced by broilers during transport and a 4 h lairage period were recorded for 8 loads of birds to 2 processing plants under summer and winter conditions. 2. During the transport period the thermal environment was considered not to have been a significant challenge to bird welfare. 3. During the lairage period, over all 8 d, external ambient temperatures were in the range 4 degrees to 15 degrees C during the winter trials and 12 degrees to 29 degrees C during the summer. Temperatures amongst the crated birds for this period were in the range 16 degrees to 29 degrees C and 20 degrees to 31 degrees C during the winter and summer trials respectively. 4. Air velocity measurements at bird level indicated air movement was of small magnitude (typically < 0.1 m/s) and of variable direction, despite the large air movements around the modules with speeds of over 1 m/s. 5. The potentially stressful thermal environments observed during lairage were achieved rapidly (< 1 h) after unloading. It is considered, therefore, that the minimisation of holding time alone is not a suitable control strategy. 6. The use of water-misting sprays as a control strategy in one lairage was observed to lower the temperature throughout the lairage but raised the humidity, which might offset the temperature advantage to the birds' thermoregulatory ability. 7. More closely controlled environments for broiler lairage facilities are suggested, with further work to increase air movement at bird level.

Air Movements↗
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↗
PubMed1996

Air movement around a worker in a low-speed flow field.

A knowledge of the air movement around a worker in a low-speed airflow is important in a number of areas: containment testing of fume cupboards; testing of personal dust samplers; testing of LEV effectiveness; and measurement of worker exposure. Measurements of velocity vectors around the upper torsos of manikins and a human in low-speed airflows have been made using a laser Doppler anemometer. Both heated and unheated manikins, as well as a 'breathing' manikin were used. The results show that quite distinctive flow patterns develop with heated and unheated bodies. Comparison of the flows around two- and three-dimensional manikins with that around a human shows that only a three-dimensional heated manikin gives good results. The unheated breathing manikin gave results which were unrepresentative of the real situation. A suitable manikin for use in sampling or testing in low-speed airflows would have a heated, rounded, three-dimensional body of reasonably human dimensions and would be non-breathing and clothed.

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↗
PubMed2004

Computational fluid dynamics and room air movement.

UNLABELLED: Computational Fluid Dynamics (CFD) and new developments of CFD in the indoor environment as well as quality considerations are important elements in the study of energy consumption, thermal comfort and indoor air quality in buildings. The paper discusses the quality level of Computational Fluid Dynamics and the involved schemes (first, second and third order schemes) by the use of the Smith and Hutton problem on the mass fraction transport equation. The importance of "false" or numerical diffusion is also addressed in connection with the simple description of a supply opening. The different aspects of boundary conditions in the indoor environment as, e.g., the simulation of Air Terminal Devices and the simulation of furnishings and occupants are discussed. The prediction of the flow in a room with a three-dimensional wall jet by the use of different turbulence models such as the k-epsilon model, the V2-f model and the Reynolds Stress model is addressed in the last chapter of the paper. PRACTICAL IMPLICATIONS: The use of computational Fluid Dynamics as a practical design method for room air distribution is widespread. It is important to consider the quality of the predictions in order to obtain a sufficient level of accuracy. It is also important to work with a practical description of supply openings as well as with the right level of details in the occupied zone and the right turbulence model. All these aspects are addressed in the article.

Air Movements↗