WORKING FOR A HEALTHY FUTURE

INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

Revisiting the effect of room size and general ventilation on the relationship between near and far-field concentrations

John W Cherrie1, Laura MacCalman1, Wouter Fransman2, Erik Tielemans2, Martin Tischer3, Martie van Tongeren1

1. Institute of Occupational Medicine, UK.

2. TNO Quality of Life, The Netherlands, The Netherlands.

3. Federal Institute for Occupational Safety and Health (BAuA), Germany.

Summary…

• The need to account for dispersion in exposure models

• Recap on the earlier work published in 1999• Extension of the modeling to: • short-term work, • batch activities and • aerosols

• Discussion of the use of the new results and the necessity for further work

Modeling approaches for dispersion…

VFF

VNF

QFF

QNF

eT

Validity of the 2-compartment model…

Nicas and Neuhaus (2008), Spencer and Plisko (2007), Nicas et al (2006).

r2= 0.94

Dispersion - NF

Continuous emission480 min

Dispersion - FF

Continuous emission480 min

Short-term work

Emission 10 min – 480 min

Simulation 480 min

NF only

30 m3 room

Short-term work

Emission 60 min and 480 min

Simulation 480 min

NF only

Aerosols…

• Based on data from Schneider et al (1999)

• Incorporate an additional term in the equations for losses to surfaces

€

N eq,FF =Vc + Vf( )

H+2 × Vw × L +W( )( )

(L ×W )

Aerosols…

Emission 480 min

Simulation 480 min

NF only

30 m3 room

Use of these data in ART…

• The data will be used to adjust predicted exposure dependant on:• volume, air change rate and • aerosol versus gas/vapour/fume

• Use generic descriptors, e.g. large well-ventilated, small confined etc.

• Current implementation simpler

Conclusions…

• This is a helpful approach that can account for dispersion in the local environment in a room

• There are still several aspects that should be further investigated:• Deposition of vapours onto surfaces• The effect of mixing of contaminants near sources• The importance of worker behaviour • Mixing in large complex rooms• Directional emission of contaminants