Email updates

Keep up to date with the latest news and content from Malaria Journal and BioMed Central.

Open Access Research

Airflow attenuation and bed net utilization: observations from Africa and Asia

Lorenz von Seidlein1*, Konstantin Ikonomidis2, Rasmus Bruun2, Musa Jawara3, Margaret Pinder34, Bart GJ Knols5 and Jakob B Knudsen2

Author Affiliations

1 Menzies School of Health Research, John Mathews Building (Bldg 58), PO Box 41096, Casuarina, NT, 0810, Australia

2 Det Kongelige Danske Kunstakademis Skoler for Arkitektur, Design og Konservering – Arkitektskolen, Copenhagen, Denmark

3 The Medical Research Council Laboratories, Fajara, The Gambia

4 London School Hygiene and Tropical Medicine, London, UK

5 In2Care BV, Wageningen, The Netherlands

For all author emails, please log on.

Malaria Journal 2012, 11:200  doi:10.1186/1475-2875-11-200

Published: 15 June 2012

Abstract

Background/Methods

Qualitative studies suggest that bed nets affect the thermal comfort of users. To understand and reduce this discomfort the effect of bed nets on temperature, humidity, and airflow was measured in rural homes in Asia and Africa, as well as in an experimental wind tunnel. Two investigators with architectural training selected 60 houses in The Gambia, Tanzania, Philippines, and Thailand. Data-loggers were used to measure indoor temperatures in hourly intervals over a 12 months period. In a subgroup of 20 houses airflow, temperature and humidity were measured at five-minute intervals for one night from 21.00 to 6.00 hrs inside and outside of bed nets using sensors and omni-directional thermo-anemometers. An investigator set up a bed net with a mesh size of 220 holes per inch2 in each study household and slept under the bed net to simulate a realistic environment. The attenuation of airflow caused by bed nets of different mesh sizes was also measured in an experimental wind tunnel.

Results

The highest indoor temperatures (49.0 C) were measured in The Gambia. During the hottest months of the year the mean temperature at night (9 pm) was between 33.1 C (The Gambia) and 26.2 C (Thailand). The bed net attenuated the airflow from a minimum of 27% (Philippines) to a maximum of 71% (The Gambia). Overall the bed nets reduced airflow compared to un-attenuated airflow from 9 to 4 cm sec-1 or 52% (p < 0.001). In all sites, no statistically significant difference in temperature or humidity was detected between the inside and outside of the bed net. Wind tunnel experiments with 11 different mesh-sized bed nets showed an overall reduction in airflow of 64% (range 55 - 71%) compared to un-attenuated airflow. As expected, airflow decreased with increasing net mesh size. Nets with a mesh of 136 holes inch-2 reduced airflow by 55% (mean; range 51 - 73%). A denser net (200 holes inch-2) attenuated airflow by 59% (mean; range 56 - 74%).

Discussion

Despite concerted efforts to increase the uptake of this intervention in many areas uptake remains poor. Bed nets reduce airflow, but have no influence on temperature and humidity. The discomfort associated with bed nets is likely to be most intolerable during the hottest and most humid period of the year, which frequently coincides with the peak of malaria vector densities and the force of pathogen transmission.

Conclusions

These observations suggest thermal discomfort is a factor limiting bed net use and open a range of architectural possibilities to overcome this limitation.

Keywords:
Malaria; Bed nets; Africa; Tanzania; The Gambia; Asia; Thailand; Philippines; Airflow; Temperature; Humidity; Climate