Risk-ranking the criticality of each space with required temperature, pressure and humidity will guide the testing procedures and excursion response times. The ventilation management committee (VMC) should take the responsibility of establishing time frames for testing procedures and response times. For example, the pressure, temperature and humidity within an operating room might be ranked by the VMC as a Category 1 risk. 

However, in a clean utility room, the pressure might be ranked a Category 2, and the temperature and humidity might be ranked a Category 4 since the pressurization is critical but not life-threatening, and the temperature and humidity would have no effect on a patient. Once space element criteria are ranked, the risk ranking can help determine testing frequencies and response times. 

As an example, at Children’s Health in Dallas, the VMC has determined that Category 1 rankings should be tested daily or weekly, depending on the building automation system monitoring in place; Category 2 rankings should be monthly or quarterly; Category 3 should be quarterly or annually; and Category 4 are to be tested as needed. 

The risk rankings also should be used to prioritize the response times when excursions occur. For example, at Children’s Health, a Category 1 requirement should be responded to within four hours and if it cannot be resolved within 24 hours the infection control department should determine if the room should be blocked until it is compliant. A Category 2 may be out of range for 24 hours, Category 3 for 48 hours and a Category 4 could be out of range for up to 96 hours.

Again, the established VMC should decide on the testing frequencies and excursion response times for each risk ranking. The table on page 42 shows a portion of Table 7.1 of the 2008 edition of American National Standards Institute/ASHRAE/American Society for Health Care Engineering Standard 170, Ventilation of Health Care Facilities, that has been risk-ranked.