Table 4.
Comparison of various standards for HVAC in ICUs across the world
| Country | Recommendation society/association (reference) | Temperature | Relative humidity | Filtration | Pressurization | Air change (outside air/total) per hour [ACH] | Specific highlights/key differences |
|---|---|---|---|---|---|---|---|
| Type of ICU—general | |||||||
| Australia | QHFG [5] | 21–24 °C | 30–60% | G4–F8 | Positive | 2/6 |
Filtration: Standards varied from MERV 7–8 to MERV 15. Few recommend HEPA filters (MERV ≥ 17). Pressurization: Positive pressure inside the ICU zone is recommended by Australian, UAE and UK societies, while neutral pressure is recommended in Germany, India, USA and recent UK HTM 2025. Temperature: Wide range varying from 16 to 25 °C. Relative humidity: Majority suggests 30–60% range whereas Indian and German recommendations remain silent. ACH: HTM 2025 (UK) strongly discourages the use of re-circulation type HVAC, presumably to avoid recirculation of airborne pathogens. Air distribution pattern: There exists no specific recommendation of air distribution pattern |
| Germany | VDI [6] | – | – | F9 | Neutral | – | |
| India | ISCCM [7, 8] | 16–25 °C | – | 99% efficiency till 5 μm | Neutral | 2/6 | |
| UAE | DHA [9] | 21–24 °C | 30–60% | HEPA | Positive | 2/6 | |
| UK | DHF [10, 11] | 18–25 °C | – | F7 | Positivea | 10 (total)b | |
| UK | HTM 2025 [12] | 20–22 °C | 40–60% | – | Neutral | 100% FA | |
| USA | AIA [13] | 21–24 °C | 30–60% | – | Neutral | 2/6 | |
| USA | ASHRAE [14] | 21–24 °C | 30–60% | – | Neutral | 2/6 | |
| Type of ICU—burn | |||||||
| Australia | QHFG [5] | 21–32 °C | 30–95% | G4–F8 | Positive | 3/6 |
Filtration: Australian recommendations suggest filtration similar to general ICUs whereas the USA recommends HEPA filtration of incoming air. Pressurization: Positive pressure isolation is recommended by Australia and the USA, whereas the rest have no mention. Temperature: Higher range (21–32 °C), in comparison to general ICU, is recommended by QHFS. Relative humidity: Higher range (up to 95%), in comparison to general ICU, is recommended by ASHRAE. Air distribution pattern: It should be ‘laminar’, as recommended by ASHRAE. |
| USA | ASHRAE [14] | – | 40–60% | HEPA | Positive | 3/6 | |
| Type of ICU—neonate | |||||||
| Australia | QHFG [5] | 22–26 °C | 30–60% | G4–F8 | Positive | 2/6 |
Filtration: There is no mention of air filtration standards by the USA whereas Australia suggests similar filtration standards as general ICUs. Pressurization: Australian recommendations suggest positive pressure whereas the USA recommends neutral pressure Temperature: Slight higher range (22–26 °C) is recommended in comparison to other ICUs. Relative humidity: Neonates having similar RH as in adults is a concern Air distribution pattern: There exists no specific recommendation of air distribution pattern |
| USA | ASHRAE [14] | 22–26 °C | 30–60% | – | Neutral | 2/6 | |
ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, AIA American Institute of Architects, VDI Verein Deutscher Ingenieure (German engineers association), UAE United Arab Emirates, DHA Dubai Health Authority, DHF Department of Health Estates and Facilities Division, HTM Health Technical Memorandum, QHFG Queensland Health Facility Guideline, ISCCM Indian Society of Critical Care Medicine, HEPA high-efficiency particulate air filter, G4 (general filter) filters for coarse dust particles which are efficient for particles ≥ 10 μm (equal to MERV 7 and 8 ASHRAE), F8 and F9 (fine filters) filters for fine particles which efficient for particles ≥ 1 μm (F8 equal to MERV 14, F9 equal to MERV 15–16), F7 fine filter with up to 99% efficiency till 5 μm, MERV Minimum Efficiency Reporting Value, FA fresh air
aIsolation room may be of negative pressure
bWhere highly infective or vulnerable patients like burns and immune deficiency are regularly admitted and at least 15 ACH are recommended