Fluid dynamics of cytotoxic safety cabinets.

This study investigated the specific fluid dynamics characteristics of cytotoxic safety cabinets (CSC), particularly those used in cancer drug reconstitution operations. Measurements taken on site were used to derive characteristic data for these cabinets. An in-depth laboratory investigation of airflows inside another CSC was also conducted. Anemometric values recorded on these two installations enabled the experimental validation of computational fluid dynamics methods applied to CSC. The digital flow simulations conducted provide a better understanding of the detailed flow structure inside a CSC and made it possible to study the influence of different operating parameters on the air velocity distribution inside the cabinet front opening: recycled air temperature, product protection airflow rate, suction openings spatial distribution, air compensation mode and draughts, operator arm penetration, and operator presence in front of the cabinet.

A numerical method of reconstructing the pollutant concentration field in a ventilated room.

Pollutant source emission flow rates in the workplace are typically unknown in occupational hygiene. Similarly, a restricted number of concentration measurements can provide only spatial limited information on the pollutant distribution in the room. This paper presents a numerical method to evaluate the intensities of pollutant sources and to reconstruct the associated concentration field at every point of a ventilated enclosure containing one or several pollutant sources of unknown emission rate. This reconstructed concentration field is obtained both from the geometric and ventilation characteristics of the enclosure and from a limited number of fixed-station concentration measurements. The method is currently applicable to steady situations. The predictions obtained are then compared with concentration measurements in a laboratory closed cabin under controlled ventilation. Pollutant sources generated tracer gas emissions at known flow rates. Comparisons were performed successively for three different physical configurations.

Evaluating age from arbitrary forms of injection functions of tracer.

The age of the air in a room is normally determined either from a pulse response or from a step change response (up or down). There are a certain number of problems involved in applying these two theoretical models, especially those associated with the duration of the injection, which must either be infinitely short or infinitely long. A hybrid method that consists of injecting a known quantity of tracer for a given time offers the advantages of both methods. The equation for calculating age is exact, regardless of the type of flow considered, and is derived from the expressions already established for a pulse response to which a correction is included to account for the tracer generation function. If a rectangular pulse is used for the injection, the solution is particularly simple.