Table 1 rRT-PCR analysis of samples from filters and swabs in the ventilation system at the 8th floor, top level of the hospital building.

Corresponding floor	Exit airflow from ward (m³/s)	Approximate distance from ward to top floor filters (m)	Sample	PCR results (Ct value)
Corresponding floor	Exit airflow from ward (m³/s)	Approximate distance from ward to top floor filters (m)	Sample	N gene	E gene
Top floor air vent samples
Covid-19 outpatient clinic	2.45	56	Ventilation shaft swab	Negative	Negative
			Air vent filter sample 1	37.13	37.30
			Air vent filter sample 2	Negative	Negative
			Air vent filter sample 3	38.79	36.96
			Cell medium in petri dish	Negative	Negative
Covid-19 ward 1	2.27	53	Ventilation shaft swab 1	Negative	Negative
			Ventilation shaft swab 2	Negative	Negative
			Air vent filter sample 1	36.86	34.91
			Air vent filter sample 2	36.31	34.87
			Air vent filter sample 3	35.32	35.41
			Cell medium in petri dish	Negative	33.00
Covid-19 ward 2	2.55	49	Ventilation shaft swab	Negative	Negative
			Air vent filter sample 1	37.42	38.70
			Air vent filter sample 2	35.72	33.85
			Air vent filter sample 3	36.72	36.08
			Cell medium in petri dish	35.32	33.16
Ground level non-patient care area	3.48	60	Air vent filter sample × 3 (negative control)	Negative	Negative

Samples not exhibiting fluorescence above threshold level after 45 PCR cycles are labeled “negative”.
Ct: cycle threshold, N gene: SARS-CoV-2 Nucleocapsid gene, E gene: SARS-CoV-2 Membrane Small Envelope gene.

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