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Supplementary Materials
The following are available online at https://www.mdpi.com/1424-8220/21/1/50/s1.
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Author Contributions
The authors confirm contribution to the paper as follows: Interoperable IoCT study conception and design based on OGC standards: S.H.L.L. and S.S.; COVID-19 risk assessment: S.S. and J.S.; Contact tracing algorithm and cleaning app S.O. and J.S.; Smart camera sensors: S.H. and M.M.J.; Smart audio sensors: S.K. and S.H.; Data collection, demo visualization, analysis and interpretation of results: S.S.; S.O., S.H., S.K., S.S. took the lead in writing the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding
This research received no external funding.

Institutional Review Board Statement
Not applicable.

Informed Consent Statement
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Data Availability Statement
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Conflicts of Interest
The authors declare no conflict of interest.