Introduction

NPL offers testing and calibration of pumped adsorption and passive diffusive samplers used for occupational exposure or ambient air quality measurements.

The DTI's Controlled Atmosphere Test Facility (CATFAC) at NPL can generate test atmospheres over extended periods (from hours to weeks) to meet different customer requirements. The aerodynamic design of the wind tunnel ensures that all samplers are dosed under identical environmental conditions.

Customer Services

The CATFAC may be employed to underpin customer sampler measurements including:

• Determination of accurate diffusive tube uptake rates
• Validation of different sorbents
• Determination of non linear effects due to concentration saturation
• Response in the presence of interfering chemical species
• Gaseous calibrated tubes as an alternative to liquid spiking

CATFAC schematic (click to enlarge)

Measurements

Continuous monitoring of the gas concentrations is obtained by:

• Gas chromatography for hydrocarbons
• Chemiluminescence for the oxides of nitrogen
• Ultra-violet fluorescence for sulphur dioxide

Calibration of the atmosphere is traceable to NPL primary gravimetric gas standards, which are regularly intercompared with those of other standards laboratories worldwide.

Sampler Types

The CATFAC can simultaneously accommodate pumped and passive tubes of all types including Perkin-Elmer, Radiello, Palmes and Dräger Orsa, in sufficient numbers to ensure a statistically representative sample for the customer.

Specification of CATFAC

The Facility is able to produce single or multiple component controlled atmospheres, at known concentrations from sub parts per billion up to parts per million, under a range of environmental conditions including:

• Temperature : 5°C to 40°C.
• Wind-speed : 0 m·s^-1 to 5 m·s^-1
• Humidity : 0% to 80% Relative Humidity
• Laminar or turbulent air-flow

Test atmospheres can include: benzene, toluene, xylenes (BTX), 1,3 butadiene, formaldehyde, oxides of nitrogen (NO_x), sulphur dioxide (SO₂), or a range of other compounds to suit requirements.

Contact

For further information about this service, please check our contacts page.