Table 1.

Total aerosol concentration recorded by the Aerodynamic Particle Sizer (APS)^* and Mini Wide Range Aerosol Sizer (MiniWRAS)^† spectrometers during the tracheostomy^‡

Activity	Particles per mL								Number of samples taken
	Mean		10th %		90th %		Maximum
	MiniWRAS	APS	MiniWRAS	APS	MiniWRAS	APS	MiniWRAS	APS	MiniWRAS	APS
1. Background empty theatre (overnight)	29	0.001	11	0.000	46	0.003	188	0.019	360	1080
2. Theatre preparation (all staff present)	32	0.020	15	0.009	50	0.035	57	0.057	23	69
3. Bipolar diathermy	136	0.997	51	0.092	187	2.671	468	4.828	15	45
4. Bronchial intubation	209	0.594	-	0.035	-	1.407	-	1.790	2	4
5. Tracheal incision	48	0.029	-	0.028	-	0.031	-	0.032	1	3
6. Brief circuit disconnect	60	0.018	-	0.013	-	0.023	-	0.025	1	3
7. Patient moved to ICU bed	41	0.089	-	0.020	-	0.035	-	0.038	1	3
8. Patient and staff leave	26	0.100	-	0.064	-	0.117	-	0.126	1	3
9. Background stabilised theatre 30 min after surgery	15	0.001	-	0.087	-	0.115	-	0.120	1	3

ICU = intensive care unit.

^*GRIMM Aerosol Technik, Ainring, Germany.

^†TSI, Shoreview, MN, USA.

^‡APS particle size measurement from > 0.37 μm. The MiniWRAS 1371 spectrometer was used to determine the concentration of smaller particles (0.01–0.37 μm). Statistics were not shown when the number of samples was low.1, 2