Raimo Niemelä

THE EFFECT OF AIR TEMPERATURE ON LABOUR PRODUCTIVITY IN CALL CENTRES-A CASE STUDY

Abstract The aim of this paper was to investigate the effect of air temperature on labour productivity in telecommunication offices. The study was conducted as a case study in two call centres because the work in the call centres can be considered to represent typical activities in the telecommunication industry. The study design consisted of an observational approach and an intervention approach. In Call Centre I, the productivity between two zones with temperature difference was compared. In Call Centre II, the intervention was conducted by installing cooling units to lower high temperature in the summer. Productivity was monitored both before and after the intervention, and it was measured as labour productivity by monitoring the number of telephone calls divided by the active work time. The indoor climate of both call centres was determined by measuring thermal climate and concentrations of relevant air pollutants as well as the acoustical environment and lighting levels. The study shows that productivity may fall by 5–7% at the elevated indoor temperatures.

Emission of Ozone and Organic Volatiles from a Selection of Laser Printers and Photocopiers

To estimate the impact of office equipment on the quality of indoor air, the emission of ozone and organic volatiles was measured from one photocopier and four laser printers, three of which operated according to traditional corona discharge technology. The laser printers equipped with traditional technology emitted significant amounts of ozone and formaldehyde. Lesser amounts of other volatile aldehydes were emitted during printing. The photocopier emitted mainly ozone. In a well-ventilated office environment, the amounts encountered here for individual volatiles were within recommended maximum exposure limits for a reasonable density of printers. Because it is not known whether the concentration of irritating volatiles, such as formaldehyde, should be kept lower in an ozone rich environment or not, and because emissions in the immediate vicinity of the printers exceeded recommendations, the authors recommend that laser printers equipped with the traditional corona rods not be placed beside or immediately at the working site of office personnel. This way, ozone concentrations can be kept below recommended maximum exposure limits, provided that the ventilation rate is adequate. Further, it seems that if a reliable quantitative comparison of total organic volatiles prior to and during printing is to be made, the inertness of the sorbent toward ozone should be confirmed.

Contaminant dispersion in the vicinity of a worker in a uniform velocity field

The transportation of gaseous contaminant from a low and moderate low impulse (momentum<1 m s(-1)) source to the breathing zone was studied in a uniform air stream flow. Results of the effects of the direction and the velocity of principal air flow, convection due to a human body, arm movement of a human being and the type of source on the concentration profiles are presented. Three important results were obtained. Firstly, for a given low and moderate impulse low impulse contaminant source in the near field of a worker, his/her orientation relative to the principal air flow direction is the most important factor in reducing occupational exposure, with an air velocity of about 0.3 m s(-1). Secondly, the effect of convection resulting from body heat on air flow was lower than expected. Thirdly, arm movements influence contaminant dispersion, and should be included when models assessing exposure are developed. The present data can also be used to validate existing computational fluid dynamic (CFD) models.

Turbulence correction for thermal comfort calculation

Abstract Thermal comfort in ventilated spaces depends mainly on air temperature, air speed and turbulence intensity. Mean air speed is commonly measured with omnidirectional hot sphere sensors, whereas directionally sensitive measurement instruments and CFD-simulations normally give the mean velocity vector. The magnitude of the mean velocity vector in turbulent room air flows can be much lower than the mean air speed due to different time averaging processes. This paper studies the difference both experimentally and theoretically as a function of turbulence intensity. A correction method was developed for calculating estimates for omnidirectional mean air speed and turbulence intensity from directional air velocity data. The method can be applied to the calculation of draught risk and thermal comfort from CFD-simulation results.

Control of Styrene Exposure by Horizontal Displacement Ventilation

Abstract The performance of a ventilation system for controlling airborne styrene exposure in lamination rooms has been evaluated. The system was designed to create a horizontal displacement flow in a tunnellike space. The effectiveness of the system was evaluated by conventional exposure measurements and with direct reading instruments. The instruments were used for studies of the distribution of styrene as well as with the PIMEX® and GridMap methods. The ventilation system was studied during manual lamination of up to 5-m long boat part molds. The time-weighted average concentrations of styrene ranged from 4.7 to 11 ppm. The results showed that an acceptable level of exposure was attained if work practices were also good. The video films made with the PIMEX method showed that exposure peaks representing only 10 percent of exposure duration accounted for one-third of the exposure. These peaks can be avoided to a certain extent if the worker is aware of them. In this instance, good work practices included...

Extent of the Reverse Flow Wake Region Produced by a Body in a Uniform Flow Field

A reverse flow is created in front of an object placed in a uniform air stream that originates from behind the object. Gaseous contaminants may then be transported into the breathing zone of a worker from sources located within the reverse flow region. This should be taken into consideration when local ventilation systems are designed. The objective of this study was to characterize the reverse flow zone created in front of a worker in a uniform flow of air,using both experimental data and numerical simulation. Experiments were carried out by moving a point contaminant source on a table placed in front of the worker, and by measuring the contaminant concentration at nose level in front of the worker. The experimentally estimated length of the reverse flow region was smallest (0.5-1.0 m) with a nominal freestream velocity of 0.1 m/s, and similar (1.1-1.4 m) with nominal freestream velocities of 0.3 and 0.5 m/s.

Stratification of welding fumes and grinding particles in a large factory hall equipped with displacement ventilation

The purpose of the study was to investigate the performance of displacement ventilation in a large factory hall where large components of stainless steel for paper, pulp and chemical industries were manufactured. The performance of displacement ventilation was evaluated in terms of concentration distributions of welding fumes and grinding particles, flow field of the supply air and temperature distributions. Large differences in vertical stratification patterns between hexavalent chromium (Cr(VI)) and other particulate contaminants were observed. The concentration of Cr(VI) was notably lower in the zone of occupancy than in the upper part of the factory hall, whereas the concentrations of total airborne particles and trivalent chromium (Cr(III)) were higher in the occupied zone than in the upper zone. The stratification of Cr(VI) had the same tendency as the air temperature stratification caused by the displacement flow field.

Assessment of horizontal displacement flow with tracer gas pulse technique in reinforced plastic plants

Abstract Displacement ventilation systems are usually based on thermal stratification due to buoyancy forces generated by warm processes in industrial buildings. However, there are many processes in which contaminant emission and heat generation are not coupled together, e.g. lamination of glass-fibre reinforced polyester products. In order to control air contaminants in processes like this, a displacement flow created horizontally across a room may be useful. This study evaluates the performance of a horizontal displacement ventilation system in two lamination rooms where reinforced plastic boats up to 17 m in length are manufactured. The tracer gas pulse technique was used to measure air change efficiency, local air change index and contaminant removal effectiveness.

Particle Concentration Profile in a Vertical Displacement Flow: A Study in an Industrial Hall

The effect of displacement flow on the distribution of aerosol concentration was investigated in an industrial hall. According to the displacement ventilation principle, vertical upflow is accomplished by introducing fresh air, cooler than room air, into the occupied zone near floor level. The fresh air is introduced from low-velocity devices and heated by warm processes. This technique allows warm air contaminants to rise to the ceiling, and the rising plume is then exhausted close to the ceiling. This study presents the results of a field study conducted in an industrial environment. The aerosol properties and behavior, especially the vertical gradients, are characterized in a displacement flow field. The results indicate that the fine particles, less than 1 microm in diameter, are transported away from the breathing zone by the ventilation process. However, the air quality is significantly influenced by the emission source, and therefore the number concentration of fine and ultrafine (smaller than 0.1 microm in diameter) aerosol particles in the breathing zone was clearly elevated compared to that of the incoming clean air. The vertical gradients displayed clear size dependence; the strongest gradients were found for particles between 0.003 and 0.015 microm in diameter.

Target Levels—Tools for Prevention

Although occupational exposure limits are sought to establish health-based standards, they do not always give a sufficient basis for planning an indoor air climate that is good and comfortable for the occupants in industrial work rooms. This paper considers methodologies by which the desired level, i.e., target level, of air quality in industrial settings can be defined, taking into account feasibility issues. Risk assessment based on health criteria is compared with risk-assessment based on “Best Available Technology” (BAT). Because health-based risk estimates at low concentration regions are rather inaccurate, the technology-based approach is emphasized. The technological approach is based on information on the prevailing concentrations in industrial work environments and the benchmark air quality attained with the best achievable technology. The prevailing contaminant concentrations are obtained from a contaminant exposure databank, and the benchmark air quality by field measurements in industrial work rooms equipped with advanced ventilation and production technology. As an example, the target level assessment has been applied to formaldehyde, total inorganic dust and hexavalent chromium, which are common contaminants in work room air.