The US and UK have been called two countries "separated by a common language". Design practices in hospital ventilation systems may be a perfect example. While many practices are similar, there are substantial differences. The US standard is ASHRAE 170-2013, Ventilation for Health Care Facilities (S170). The UK standard is Healthcare Technical Memorandum 03-01: Specialized ventilation for healthcare premises (HTM 03-01). This paper provides an overview of similarities and differences between the two standards. It examines requirements of S170, and seeks out comparable requirements in HTM 03-01. The authors hope that the US standard can incorporate learnings, and capture best practices from its UK counterpart. Some key findings are:

1. S170 may, in the long run, benefit from more explanation, particularly around infection control, and how healthcare ventilation relates to other non-residential ventilation practices.
2. Specialty ventilation may be over-applied in S170. Many spaces covered may be responsibly ventilated by the normal, non-residential design practices.
3. Filtration of air may also be over-specified in S170 in less critical areas. Appropriate sources of clean air could be re-assessed, including natural ventilation.
4. Design of isolation spaces might be improved by adopting the hierarchy of cleanliness, emphasis on clean air path, and design for open door conditions.
5. S170 might augment its benifit to the quality of the patient environment by referencing or considering acoustics, and a more conventional comfort design approach.
6. Humidification may be over-applied in S170. Specific clarifications of humidity non-comfort affects could be helpful.
7. Cross-contamination of air in energy recovery devices may be over-regulated.
8. A stronger recommendation for commissioning of health care ventilation systems might be considered. In particular, testing to assure operating room air cleanliness seems prudent.
9. Appendices and recommendations for operations could be stronger.