Rauno Holopainen

Perceived indoor air quality, air-related symptoms and ventilation in Finnish hospitals

ObjectivesGood ventilation is more important in hospitals than in many other buildings. The objective of this study was to evaluate the effect of the condition, performance and modernity of ventilation systems on the perceived indoor air quality (IAQ) and the indoor air-related symptoms of hospital personnel.Materials and MethodsAn inspection and evaluation graded on a 1 to 3 scale of the condition, performance, and modernity of the ventilation systems was carried out in ten central hospitals in Finland. The perceived IAQ and the related symptoms were collected by means of an indoor air questionnaire survey among the workers in these hospitals.ResultsThe condition, performance and modernity of the ventilation systems were good in 40% of the hospitals included in the research and poor in another 40% of them. In hospitals where the majority of the ventilation systems were assessed to be good, the prevalence of the indoor air-related complaints and symptoms was lower than in hospitals where the majority of the ventilation systems were assessed as needing extensive repairs.ConclusionsThe condition and performance of the ventilation systems in hospitals had a significant impact on the perceived IAQ and the symptoms observed among the employees in Finnish hospitals. Therefore, it is important that hospital ventilation systems are maintained properly and regularly. Furthermore, they should be renovated, at the latest when their technical lifespan expires.

Intelligent HVAC systems in hospitals

Increasing interest has been expressed towards intelligent heating, ventilation and air conditioning (HVAC) systems in hospital environments. This article presents a literature review of intelligent HVAC systems used in hospitals. First, we discuss the current state of HVAC systems and common ventilation issues regarding modern hospitals. Second, we describe hospital airflow modelling using computational fluid dynamics. We then define ‘intelligent HVAC systems’ and address challenges concerning their design and implementation. Lastly, possibilities for HVAC system optimization and energy conservation are presented.

Crawling-induced floor dust resuspension affects the microbiota of the infant breathing zone

BackgroundFloor dust is commonly used for microbial determinations in epidemiological studies to estimate early-life indoor microbial exposures. Resuspension of floor dust and its impact on infant microbial exposure is, however, little explored. The aim of our study was to investigate how floor dust resuspension induced by an infant’s crawling motion and an adult walking affects infant inhalation exposure to microbes.ResultsWe conducted controlled chamber experiments with a simplified mechanical crawling infant robot and an adult volunteer walking over carpeted flooring. We applied bacterial 16S rRNA gene sequencing and quantitative PCR to monitor the infant breathing zone microbial content and compared that to the adult breathing zone and the carpet dust as the source. During crawling, fungal and bacterial levels were, on average, 8- to 21-fold higher in the infant breathing zone compared to measurements from the adult breathing zone. During walking experiments, the increase in microbial levels in the infant breathing zone was far less pronounced. The correlation in rank orders of microbial levels in the carpet dust and the corresponding infant breathing zone sample varied between different microbial groups but was mostly moderate. The relative abundance of bacterial taxa was characteristically distinct in carpet dust and infant and adult breathing zones during the infant crawling experiments. Bacterial diversity in carpet dust and the infant breathing zone did not correlate significantly.ConclusionsThe microbiota in the infant breathing zone differ in absolute quantitative and compositional terms from that of the adult breathing zone and of floor dust. Crawling induces resuspension of floor dust from carpeted flooring, creating a concentrated and localized cloud of microbial content around the infant. Thus, the microbial exposure of infants following dust resuspension is difficult to predict based on common house dust or bulk air measurements. Improved approaches for the assessment of infant microbial exposure, such as sampling at the infant breathing zone level, are needed.

Notes on Junction Coefficients

Abstract Application of the principle of the balance of mechanical energy gives a constraint on the possible values of the junction coefficients at a duct system junction. In some cases the recorded junction coefficients in the literature do not satisfy this constraint. The values given may then be questionable. The terminology in connection with junctions is discussed and the role of the principle of balance of mechanical energy in duct system flow modelling is considered in some detail.

A PQ-Formulation for Ventilation Duct System Flow Analyses

Abstract A formulation to analyze ventilation duct system airflows employing, as the basic unknowns, the flow rates in the channel sections and the static pressures at the channel section ends is presented. This approach is called the PQ-formulation and the corresponding system equations are called PQ-equations. The system equations in the PQ-formulation are the engineering Bernoulli equations for the channel sections, the inlet and outlet pressure jump equations at the inlet and outlet nodes, the continuity equations at the junctions and the pressure jump equations at the junctions. The nonlinear system equations are solved by the Picard method using a relaxation factor. The linearizations employed in the Picard method are described. Special additional themes are the treatment of the updating of junction coefficients and the use of a so-called balancing factor for checking convergence. Numerical demonstration results are given in some example cases.

Air Tightness of Ventilation Ductwork in Recently Built Low-Energy and Conventional Houses

Abstract The air tightness of ventilation ductwork was measured in two recently built low-energy houses and in two conventionally built houses in the summer of 2013. The ducts and components were metal in three houses and plastic in one house. The air tightness of the ductwork had been checked by an installation survey after construction. The measured leakage airflows corresponded to air tightness class A or lower, therefore did not satisfy the minimum requirement set for class B regarding the air tightness of ventilation ductwork. Leakage airflow of the ductwork per duct surface area was estimated to be 47 times higher at a typical ventilation duct pressure of 100 Pa than leakage airflow in the house envelope per internal surface area at a typical house air pressure of 5 Pa. The results showed that the installation survey was not a sufficient method for ensuring the air tightness of ductwork in these houses. Therefore, it is recommended that the air tightness of ventilation systems that serve a single room or a single dwelling are measured during commissioning. A larger study of the air tightness of ventilation systems in Finnish buildings would be necessary.

Initial Flow Rates for Ventilation Duct System Flow Analyses

Abstract The governing equations in duct system flow analyses are nonlinear, and iterative solution methods must be used. A suitable initial flow rate guess may be needed to start the calculations so that a converged solution can be finally achieved. A method to obtain a reasonably accurate initial flow rate guess is presented. In it the duct system is analyzed first in a strongly simplified setting assuming a linear (imaginary laminar) duct flow problem. The continuity equations at the junctions are satisfied. This first initial flow rate guess is then scaled to arrive at a more realistic final initial guess. The scaling is achieved by multiplication by a so–called balancing factor which is based on the application of mechanical energy balance for the whole duct system. The junction continuity equations are still satisfied for this final initial guess. A MATLAB program was generated to perform the calculations. Two demonstration example cases are presented to show the effect of the accuracy of the initial guess on the number of necessary iteration steps in connection with a PQ–duct system flow solution formulation.

Combining Junction Losses on Channel Sections in Ventilation Duct System Flow Analyses

Abstract When the airflow pressure losses at the junctions of ducts in ventilation systems aretaken into account, the analysis becomes more complicated since no unique value for the static pressure is associated with a junction. Additional system equations expressing the pressure jumps over the junctions must be written down. A method to replace the junction losses approximately as equivalent channel section losses is presented. The method isbased on dissipation considerations. Simpler system equations with fewer unknowns are obtained. Some example cases are presented to give an idea about the errors involved.