Table 2 Applied threshold values, from human healthcare, for bacterial loads

Passive air sample during surgery

OR^a

 ≤ 19 CFU/dm²/h

Suggested mean value per surgery

Swedish guidelines

16

Passive air sample during surgery

OR

 ≤ 39 CFU/dm²/h

Suggested highest value during surgery

"

16

Passive air sample in an empty OR

OR

2 CFU/dm²/h

Suggested target value

Prospective observational study

17

Passive air sample in an empty OR

OR

5 CFU/dm²/h

Suggested alert value

"

17

Passive air sample in medium risk environments (e.g. hospital wards and outpatient clinics)

UR^b

 ≤ 79 CFU/dm²/h

Suggested threshold value

Review

18

Surface sample; high-touch and sterile field

OR

 ≤ 0.21 CFU/cm²

Suggested expected level

Italian guidelines

19

Surface sample; high-touch and sterile field

OR

 ≤ 0.63 CFU/cm²

Suggested acceptable level

"

19

Surface sample; high-touch and near-patient

UR

 < 2.5 CFU/cm²

Suggested threshold value

Prospective observational studies

20–22