Arlindo Tribess

Analysis of Thermal Comfort in an Office Environment with Underfloor Air Supply in a Tropical Climate

Research on office building environments with ceiling air distribution has demonstrated that thermal comfort has not been well promoted, with 30% of Brazilian users expressing dissatisfaction. The underfloor air supply system, which has been adopted to tackle these concerns, was evaluated in laboratories to fill the lack of information in this field. The results of this research show that thermal conditions created by this system fulfill the thermal comfort requirements. However, the operative temperature limits of discomfort are slightly higher than those adopted by ISO 7730 (ISO 1994). Parameters of thermal comfort and of system operation are presented in this paper.

A Review of Methods Applied to Study Airborne Biocontaminants inside Aircraft Cabins

Indoor-cross infection of expiratory contaminants is still a concern, worsened by the SARS outbreak in 2003 and recent cases of influenza strains (H1N1, avian flu, etc.). A variety of methods to study the airborne spread of expiratory contaminants have been worked out, including the use of tracer gas, particle generators, and CFD simulations. In this context, the main objective of this work is reviewing methods to evaluate airborne dispersion of contaminants, more specifically those related to cross infection of expiratory droplets inside aircraft cabins. This literature review provides guidance in developing methods and choosing equipment for future studies.This study gathers knowledge developed so far in a common source, serving as a guideline for researchers who work in this area.

Avaliação de conforto térmico em ambientes cirúrgicos utilizando método de Fanger e temperaturas equivalentes

Em ambientes cirurgicos as condicoes de conforto termico precisam ser as melhores possiveis para que o cirurgiao e a equipe medica trabalhem em condicoes favoraveis para o sucesso do procedimento cirurgico. Neste trabalho sao avaliadas condicoes de conforto termico em salas cirurgicas utilizando o metodo de Fanger e temperaturas equivalentes. Foram realizadas medicoes de variaveis ambientais e avaliacoes subjetivas baseadas em questionarios. A aplicacao do metodo de Fanger mostrou-se adequada na avaliacao de condicoes de conforto termico em salas cirurgicas, embora seja necessario cuidado especial em sua utilizacao e na analise dos resultados. Paralelamente, resultados de estudo comparativo com trabalhos de outros autores mostraram valores praticamente iguais de temperaturas equivalentes de conforto termico, em torno de 22 o C, para todos os membros da equipe cirurgica. Esse resultado e particularmente util para avaliar diferentes condicoes ambientais e pessoais em propiciar condicoes adequadas de conforto termico aos diferentes membros da equipe cirurgica.

Sudden temperature changes and respiratory symptoms--an experimental approach.

Background Exposure to air-conditioning systems and allergic phenotypes are consistent risk factors to develop indoor air quality (IAQ) respiratory complaints. The aim of this study was to compare the role of allergic rhinitis on respiratory complaints in individuals exposed to sudden temperature changes. Methods To address this question, a case-control challenge study was performed in a laboratory of thermal comfort evaluation with twin isolated chambers set at 14°C/57.2°F (cold) and 26°C/78.8°F (hot) temperatures. A groups of 32 patients with persistent allergic rhinitis (rhinitis group) and 16 control subjects (control group) were exposed for 30 minutes, three times alternately in the chambers. Symptoms were reported using an analog visual scale and nasal and pulmonary peak flow measurements were taken during baseline at hot and cold temperatures and after the challenge. Results The rhinitis group reported increased itching and stinging eyes when compared with the baseline during exposure to hot and cold temperatures and they also reported increased breathlessness during hot air exposure. In addition, there was a significant decrease in expiratory flow rates in this group during exposure to hot and cold temperatures that persisted for 24 hours after challenge. Conclusion This study suggests that individuals with allergic rhinitis have a lower threshold than controls to develop respiratory and ocular symptoms after air-conditioning–induced sudden temperature changes.

Gender Influences in Indoor Air Quality Perception for Individuals in Tropical Climate

Gender differences in indoor air quality perception are still controversial and geographic and climate variations can alter substantially the perceived indoor air quality. The aim of this study was to compare differences and analyze data on indoor air quality perception between genders in individuals living in the tropics. To address this question thirty-three subjects grouped by gender were exposed to 14, 18, 22 and 26 degrees Celsius (°C) - or correspondingly, 57.2, 64.4, 71.6 and 78.8 degrees Fahrenheit (F) - with a relative humidity of the indoor air of 65 ± 7% in an experimental office environment. Results were obtained by a selfadministered visual analogue scale questionnaire and analyzed using mean score comparisons and principal component analysis of indoor air perception. The results demonstrated that apart from colder temperatures far from thermoneutrality both groups showed no differences in IAQ scores and very close patterns of indoor air quality perception. This study suggests a role for other contributing factors as cultural and dressing habits as determinants to gender differences in indoor air-quality perception concerning individuals living in tropical climate.

Experimental and Numerical Analysis of the Relationship Between Indoor and Outdoor Airborne Particles in an Operating Room

This work investigated the impact of the HVAC filtration system and indoor particle sources on the relationship between indoor and outdoor airborne particle size and concentrations in an operating room. Filters with efficiency between 65% and 99.97% were used in the investigation and indoor and outdoor particle size and concentrations were measured. A balance mass model was used for the simulation of the impact of the surgical team, deposition rate, HVAC exhaust and air change rates on indoor particle concentration. The experimental results showed that high efficiency filters would not be expected to decrease the risk associated with indoor particles larger than approximately 1 µm in size because normal filters are relatively efficient for these large particles. A good fraction of outdoor particles were removed by deposition on the HVAC system surfaces and this deposition increased with particle size. For particles of 0.3–0.5 µm in diameter, particle reduction was about 23%, while for particles >10 µm the loss was about 78%. The modelling results showed that depending on the type of filter used, the surgical team generated between 93% and 99% of total particles, while the outdoor air contributed only 1–6%.

Thermal comfort and local discomfort in an operating room ventilated with spiral diffuser jet

Operating rooms often exhibit vertical temperature gradient, radiant asymmetry, local airflows, and local body cooling. The impact of these parameters on the thermal comfort of the occupants can be greatly affected by the type of air-conditioning system used in the room. This work evaluated thermal comfort conditions in an operating room ventilated with a spiral diffuser jet using an instrumented thermal manikin with heated sensors. The objective is to assess the conditions of thermal comfort and local discomfort of the patient and surgical team in this kind of environment using the concept of equivalent temperatures and a manikin with heated sensors. Additionally, the method proposed by Fanger was used to evaluate the thermal sensation. The results showed a very small change in the equivalent temperatures in different parts of the body for the surgeon and nurse. The thermal sensation for the surgeon and nurse simulated by the manikin and using a thermal comfort diagram for equivalent temperature was neutral in the whole body. However, higher equivalent temperatures were found on the heads of the surgeon and nurse because of the heat exchange by radiation from the surgical lights. The local thermal sensation for the patient varied from too cold, cold, and neutral, depending on the body part. Finally, the methodology proposed showed to be very effective for evaluating the thermal comfort conditions in operating rooms when compared to the method proposed by Fanger.

Measurement of the concentration and size of aerosol particles and identification of the sources in orthopedic surgeries

In this study, the measurement of the concentration and size of particles and the identification of their sources were carried out at five orthopedic surgeries. The aerosol concentration and particle size distribution, ranging from 0.3 μm–10 μm, were measured and related to the type of indoor activity. The handling of surgical linen and gowns, handling of the patient, use of electrosurgical apparatus, use of a bone saw, handling of equipment, and cleaning of the room were identified as the most important sources of particles, with each of these activities posing different risks to the health of the patients and workers. The results showed that most of the particles were above 0.5 μm and that there was a strong correlation among all particles of sizes above 1 μm. Particles with diameters in the range of 0.3 μm–0.5 μm had a good correlation only with particles in the ranges of 0.5 μm–1.0 μm and 1.0 μm–3.0 μm in three of the surgeries analyzed. Findings led to the conclusion that most of the events responsible for generating aerosol particles in an orthopedic surgery room are brief, intermittent, and highly variable, thus requiring the use of specific instrumentation for their continuous identification and characterization.

RISK ASSESSMENT FOR AIRBORNE INFECTIOUS DISEASES BETWEEN NATURAL VENTILATION AND A SPLIT-SYSTEM AIR CONDITIONER IN A UNIVERSITY CLASSROOM

Indoor air quality is a critical factor in the classroom due to high people concentration in a unique space. Indoor air pollutant might increase the chance of both long and short-term health problems among students and staff, reduce the productivity of teachers and degrade the student’s learning environment and comfort. Adequate air distribution strategies may reduce risk of infection in classroom. So, the purpose of air distribution systems in a classroom is not only to maximize conditions for thermal comfort, but also to remove indoor contaminants. Natural ventilation has the potential to play a significant role in achieving improvements in IAQ. The present study compares the risk of airborne infection between Natural Ventilation (opening windows and doors) and a Split-System Air Conditioner in a university classroom. The Wells-Riley model was used to predict the risk of indoor airborne transmission of infectious diseases such as influenza, measles and tuberculosis. For each case, the air exchange rate was measured using a CO2 tracer gas technique. It was found that opening windows and doors provided an air exchange rate of 2.3 air changes/hour (ACH), while with the Split System it was 0.6 ACH. The risk of airborne infection ranged between 4.24 to 30.86 % when using the Natural Ventilation and between 8.99 to 43.19% when using the Split System. The difference of airborne infection risk between the Split System and the Natural Ventilation ranged from 47 to 56%. Opening windows and doors maximize Natural Ventilation so that the risk of airborne contagion is much lower than with Split System.

Análise de desconforto térmico local em ambientes cirúrgicos com o uso de manequim, medição de variáveis ambientais e avaliação subjetiva

Na avaliacao de conforto termico em ambientes interiores nao basta analisar as condicoes de conforto para o corpo como um todo, pois ha a necessidade de se analisar tambem as condicoes de desconforto termico local. Em ambientes complexos, tais como os ambientes cirurgicos, onde os membros da equipe cirurgica ocupam diferentes posicoes no ambiente e desempenham atividades distintas, a analise de condicoes de desconforto termico local torna-se ainda mais premente. No presente trabalho foram analisadas condicoes de desconforto termico local devido a assimetrias da temperatura radiante, diferenca vertical de temperatura do ar e risco de correntes de ar utilizando manequim, medicao de variaveis ambientais e avaliacao subjetiva. Resultados da avaliacao subjetiva mostraram niveis de insatisfacao de ate 35 % dos anestesistas e enfermeiros com correntes de ar e de ate 85% dos cirurgioes com o calor do foco cirurgico. Resultados similares foram obtidos a partir da medicao de variaveis ambientais e com o uso de manequim. Estes resultados ressaltam ainda mais a grande dificuldade de se prover condicoes de conforto termico neste tipo de ambiente. Entretanto, a utilizacao de diferentes ferramentas de analise pode auxiliar na busca de se prover condicoes de conforto termico as melhores possiveis para todos os membros da equipe cirurgica.