Table 1. ACH and removal efficiencies.

ACH	Removal efficiency at 1 hour (%)	Minutes required for removal efficiency
		99%	99.9%
2	86.5	138	207
4	98.2	69	104
6	99.75	46	69
12	99.9994	23	35
20	99.99999	14	21

ACH: air changes per hour.