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Title: Comparison of two tracer gas dilution methods for the determination of clothing ventilation and of vapour resistance
Authors: Havenith, George
Zhang, Ping
Hatcher, Kent
Daanen, Hein A.M.
Keywords: Clothing ventilation
Vapour resistance
Tracer gas
Clothing microclimate volume
Issue Date: 2010
Publisher: © Taylor & Francis
Citation: HAVENITH, G. ... et al, 2010. Comparison of two tracer gas dilution methods for the determination of clothing ventilation and of vapour resistance. Ergonomics, 53 (4), pp.548–558.
Abstract: Two methods for Clothing microclimate ventilation determination (Crockford (CR), 1972 and Lotens & Havenith (LH), 1988) are compared for reproducibility, validity, and usability. Both methods showed good sensitivity and reproducibility (average coefficient of variation 1.5- 2.3% for the method, up to 7% for method and dressing/movement effects combined) and produce values close to calibration values in forced ventilation tests (r=0.988). Weak points for CR are limits in time constant of the equipment, causing an upper limit of measurable ventilation (around 800 l/min), and the measurement of clothing microclimate volume, showing large errors. Alternatives (whole body scanner or manual circumference measurements) were shown to produce good results. For LH, the distribution of the tracer gas over the whole skin surface becomes a problem factor at very high ventilations (above 1000 l/min). When the measurement is used to determine water vapour resistance, the choice of tracer gas (O2, Ar, CO2, SF6) affects results.Clothing microclimate ventilation is an important parameter in climatic stress and in contaminated environments. The two main methods for its determination (Crockford (CR), 1972 and Lotens & Havenith (LH), 1988) are, after further development, compared in terms of reproducibility, validity, and usability. Both methods are shown to have a good sensitivity and reproducibility (average Coefficient of Variation 1.5-2.3% for the method, up to 7% for method and dressing/movement effects combined) and produce values very close to calibration values in forced ventilation tests (r=0.988). Weak points for CR are the limits in the time constant of the measurement apparatus, causing an upper limit of ventilation that can be reliably measured (around 800 l/min), and the for this method required measurement of clothing microclimate volume. The original ‘vacuum oversuit’ method was cumbersome and prone to large errors. Alternatives (whole body scanner or manual circumference measurements) were shown to produce good results. For LH, the distribution of the tracer gas over the whole skin surface becomes a problem factor at very high ventilations (above 1000 l/min). As all methods use tracer gasses (O2, Ar, CO2, SF6) with diffusivities smaller than that of water vapour, this potentially creates a problem in the calculation of vapour resistance from the ventilation values in the region where the emphasis of vapour transfer moves from diffusion to convection. In most real life situations, where body and air movement are present, a correction is not required however as the error remains below 10%. Clothing microclimate ventilation is an important parameter in climatic stress and in contaminated environments. The two main methods for its determination (Crockford (CR), 1972 and Lotens & Havenith (LH), 1988) are, after further development, compared in terms of reproducibility, validity, and usability. Both methods are shown to have a good sensitivity and reproducibility (average Coefficient of Variation 1.5-2.3% for the method, up to 7% for method and dressing/movement effects combined) and produce values very close to calibration values in forced ventilation tests (r=0.988). Weak points for CR are the limits in the time constant of the measurement apparatus, causing an upper limit of ventilation that can be reliably measured (around 800 l/min), and the for this method required measurement of clothing microclimate volume. The original ‘vacuum oversuit’ method was cumbersome and prone to large errors. Alternatives (whole body scanner or manual circumference measurements) were shown to produce good results. For LH, the distribution of the tracer gas over the whole skin surface becomes a problem factor at very high ventilations (above 1000 l/min). As all methods use tracer gasses (O2, Ar, CO2, SF6) with diffusivities smaller than that of water vapour, this potentially creates a problem in the calculation of vapour resistance from the ventilation values in the region where the emphasis of vapour transfer moves from diffusion to convection. In most real life situations, where body and air movement are present, a correction is not required however as the error remains below 10%. Clothing microclimate ventilation is an important parameter in climatic stress and in contaminated environments. The two main methods for its determination (Crockford (CR), 1972 and Lotens & Havenith (LH), 1988) are, after further development, compared in terms of reproducibility, validity, and usability. Both methods are shown to have a good sensitivity and reproducibility (average Coefficient of Variation 1.5-2.3% for the method, up to 7% for method and dressing/movement effects combined) and produce values very close to calibration values in forced ventilation tests (r=0.988). Weak points for CR are the limits in the time constant of the measurement apparatus, causing an upper limit of ventilation that can be reliably measured (around 800 l/min), and the for this method required measurement of clothing microclimate volume. The original ‘vacuum oversuit’ method was cumbersome and prone to large errors. Alternatives (whole body scanner or manual circumference measurements) were shown to produce good results. For LH, the distribution of the tracer gas over the whole skin surface becomes a problem factor at very high ventilations (above 1000 l/min). As all methods use tracer gasses (O2, Ar, CO2, SF6) with diffusivities smaller than that of water vapour, this potentially creates a problem in the calculation of vapour resistance from the ventilation values in the region where the emphasis of vapour transfer moves from diffusion to convection. In most real life situations, where body and air movement are present, a correction is not required however as the error remains below 10%. Clothing microclimate ventilation is an important parameter in climatic stress and in contaminated environments. The two main methods for its determination (Crockford (CR), 1972 and Lotens & Havenith (LH), 1988) are, after further development, compared in terms of reproducibility, validity, and usability. Both methods are shown to have a good sensitivity and reproducibility (average Coefficient of Variation 1.5-2.3% for the method, up to 7% for method and dressing/movement effects combined) and produce values very close to calibration values in forced ventilation tests (r=0.988). Weak points for CR are the limits in the time constant of the measurement apparatus, causing an upper limit of ventilation that can be reliably measured (around 800 l/min), and the for this method required measurement of clothing microclimate volume. The original ‘vacuum oversuit’ method was cumbersome and prone to large errors. Alternatives (whole body scanner or manual circumference measurements) were shown to produce good results. For LH, the distribution of the tracer gas over the whole skin surface becomes a problem factor at very high ventilations (above 1000 l/min). As all methods use tracer gasses (O2, Ar, CO2, SF6) with diffusivities smaller than that of water vapour, this potentially creates a problem in the calculation of vapour resistance from the ventilation values in the region where the emphasis of vapour transfer moves from diffusion to convection. In most real life situations, where body and air movement are present, a correction is not required however as the error remains below 10%.
Description: This article was accepted for publication in the journal, Ergonomics [© Taylor & Francis]. The definitive version is available from: http://dx.doi.org/10.1080/00140130903528152
Version: Accepted for publication
DOI: 10.1080/00140130903528152
URI: https://dspace.lboro.ac.uk/2134/5596
ISSN: 0014-0139
1366-5847
Appears in Collections:Published Articles (Design School)

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