Table 1.

Comparison of main features of passive and active bioaerosol samplers.

Feature	Passive Samplers	Active Samplers
Known flow rate	No (work is ongoing to establish an equivalent flowrate)	Yes
Known sample volume	No	Yes
Airborne concentration determination	Estimate only	Yes
Sampling duration	Hours to weeks	Minutes to weeks
Primary collection mechanisms	Gravitational settling, electrostatic forces, diffusion, turbulent dispersion, opportunity-based sampling	Filtration, impaction, impingement, cyclonic forces, electrostatic forces
Power requirements	None	Pump and electrostatic components, if ESP is used
Weight	Lightweight and portable	Heavier due to addition of sampling media (e.g., agar) and a pump
Operator attention requirements	Deployment and retrieval	Deployment and retrieval, flowrate determination and maintenance, media replenishment for liquidbased samplers, possible replacement of collection media
Cost	Sampler	Sampler, pump, power supply