N.25 – European Standard for biological Agents Monitoring in workplace atmosphere

TRIO

The European Standard EN 14042, April 2003 “Workplace atmospheres – Guide for application and use of procedures for the assessment of exposure to chemical and biological agents” 6.3 “Measurement of airborne micro-organisms and endotoxin”, 6.3.1. “Methods using an impactor as sampler” presents the Table.

CHARACTERISTICS COMMENTS
   
Operating principles A measured volume of air is drawn through a sampler such that airborne micro-organisms are caused to leave the air stream and impact onto e semi solid (typically an agar culture medium) or solid surface. Semi solid media thus directly inoculated are incubated to develop colonies from viable, culturable micro-organisms
Typical measurement task Measurements near an emission source; periodic measurements
Typical measurement range 101 to 105 Colony Forming Units per 1 m3 of air
Response time/Averaging time 1 minute to 30 minutes depending on bio-aerosol concentration
Selectivity Dependent on subsequent analysis
Influence of environmentalParameter: Pressure No
Influence of environmentalParameter: Temperature and humidity Both can affect viability / culturability of bio-aerosol; could cause dehydration of semisolid collection substrates leading to reduction in collection efficiency
Influence of environmentalparameter: Air speed Effect on inlet efficiency
Influence of environmentalParameter: Vibration No
Calibration Calibrate inlet air flow rate before each sampling
Limitations Short sampling time for high bio-areosol concentrations to avoid overloading. In general can only be used for culturable analysis. High sampler costs. Static (area) sampling only. Many samplers available poorly characterised for inlet efficiency compared to ISO /CN convention