I85PREP
⌘ K
CHFM study materials
CHFM study resources

CHFM practice questions

One question at a time. Build your CHFM understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Planning, Design, and Construction

The primary purpose of the Facility Guidelines Institute (FGI) Guidelines for Design and Construction of Hospitals is to:

  1. define clinical staffing ratios for inpatient units
  2. establish reimbursement rates for construction projects
  3. prescribe the hospital accreditation survey process
  4. set minimum design and construction requirements Correct answer.

Explanation

The FGI Guidelines are consensus-based minimum standards for the design and construction of health care facilities and are adopted by many states and referenced by accreditors. They address the functional program, architectural details, and engineering systems rather than staffing, payment, or survey methods.

Question 2Planning, Design, and Construction

Which group should participate in the preconstruction risk assessment for a renovation adjacent to occupied patient care areas?

  1. A multidisciplinary team led by infection prevention Correct answer.
  2. Only the general contractor's project superintendent
  3. Only the hospital's safety officer and the architect of record
  4. The finance department and the equipment vendor

Explanation

The preconstruction risk assessment is a multidisciplinary activity in which infection prevention, facilities management, construction, and clinical staff jointly identify hazards and agree on mitigation before work starts. Limiting participation to one trade or one department leaves key risks unaddressed.

Question 3Planning, Design, and Construction

Interim life safety measures (ILSMs) are implemented when:

  1. construction compromises life safety features in occupied areas Correct answer.
  2. a new building is being designed but not yet constructed
  3. the facility's annual fire drill schedule has not been completed
  4. the facility is preparing for its routine accreditation survey

Explanation

ILSMs are temporary compensatory measures used when construction, renovation, or a system failure degrades a required life safety feature such as fire alarm, sprinklers, or egress. They remain in place until the deficient feature is restored.

Question 4Planning, Design, and Construction

Which barrier class is required for work that generates heavy dust in or near areas housing high-risk patients?

  1. Class I barrier
  2. Class II barrier
  3. Class IV barrier Correct answer.
  4. Class III barrier

Explanation

In the infection control barrier classification used with the ICRA, Class IV is the most stringent: a sealed barrier maintained under negative pressure and exhausting through HEPA filtration. It is used for high dust-generating work adjacent to the highest-risk patient populations.

Question 5Planning, Design, and Construction

Before a contractor performs welding or cutting in an occupied hospital building, the facility manager must confirm that:

  1. the contractor has renewed its certificate of insurance
  2. a hot work permit has been issued and a fire watch is in place Correct answer.
  3. the work is scheduled after normal business hours
  4. the area's sprinkler system has been shut off to prevent water damage

Explanation

Hot work such as welding and cutting requires a permit, removal of combustibles, fire extinguishing equipment, and a fire watch during and after the operation. These controls address the ignition risk that hot work introduces into an occupied building.

Question 6Planning, Design, and Construction

Which document defines the spaces, adjacencies, and operational requirements that a new health care project must satisfy?

  1. The construction schedule
  2. The life cycle cost analysis
  3. The commissioning plan
  4. The functional program Correct answer.

Explanation

The functional program is the owner's written statement of need: the services to be provided, the spaces required, their relationships, and operational assumptions. Design solutions and commissioning criteria are developed from it.

Question 7Planning, Design, and Construction

The Life Safety Code, which sets minimum requirements for egress, fire protection, and construction features in health care occupancies, is published as:

  1. NFPA 25
  2. NFPA 99
  3. NFPA 101 Correct answer.
  4. NFPA 70

Explanation

NFPA 101 is the Life Safety Code and governs egress, protection, and occupancy features. NFPA 99 covers health care facilities systems, NFPA 25 covers inspection and testing of water-based suppression, and NFPA 70 is the National Electrical Code.

Question 8Planning, Design, and Construction

The primary purpose of commissioning a new health care building is to:

  1. shorten the construction schedule and lower cost
  2. transfer risk from the contractor to the owner
  3. verify that systems perform as intended by the owner Correct answer.
  4. satisfy only the local building department's inspection requirements

Explanation

Commissioning is a quality-focused process that documents and verifies that systems and assemblies are installed and operate in accordance with the owner's project requirements and design intent. It goes beyond code inspections by testing performance across modes and loads.

Question 9Planning, Design, and Construction

An infection control risk assessment for an active construction project should be revisited when:

  1. the scope, schedule, or site conditions change during the project Correct answer.
  2. the general contractor submits the monthly payment application
  3. the owner's capital budget is revised
  4. the design team issues a sustainability scorecard

Explanation

The ICRA is a living document: changes in the scope of work, duration, dust generation, or adjacent patient populations can change the required barrier class and precautions. The assessment must be updated so mitigation matches current conditions.

Question 10Planning, Design, and Construction

When a construction enclosure is built adjacent to patients who are severely immunocompromised, air leaving the work area should be:

  1. discharged into the corridor to maintain the enclosure's pressure
  2. recirculated within the construction zone to conserve energy
  3. exhausted through a HEPA filter before discharge Correct answer.
  4. returned to the central air-handling unit without treatment

Explanation

Air from the work area must be contained and exhausted through HEPA filtration, which removes 99.97 percent of particles at 0.3 micron, preferably to the outside. This prevents dust and fungal spores from reaching highly susceptible patients.

Question 11Planning, Design, and Construction

Construction debris removed from a renovation site in an occupied hospital should be:

  1. hauled through the main lobby so the contractor can use the shortest route
  2. stored in the corridor until a full truckload accumulates
  3. transported in covered carts along routes that avoid patient care areas Correct answer.
  4. carried through patient corridors during shift change to save time

Explanation

Debris must be removed promptly in covered carts using designated routes that minimize exposure to patients and avoid contaminating clean areas. Corridors that serve as means of egress must also remain clear of stored materials.

Question 12Planning, Design, and Construction

At which design phase are drawings and specifications typically complete enough to obtain a building permit and to prepare contractor bids?

  1. Design development
  2. Programming phase
  3. Construction documents Correct answer.
  4. Schematic design

Explanation

Construction documents convey the full scope, dimensions, materials, and systems needed for regulatory review, permitting, and competitive bidding. Earlier phases establish need and concept but lack the detail required for those purposes.

Question 13Planning, Design, and Construction

Value engineering during design is best described as:

  1. a systematic review to achieve required functions at lowest cost Correct answer.
  2. deferring maintenance costs to future fiscal years
  3. selecting the lowest bidder for each individual construction trade package
  4. reducing the project scope until it fits the available budget

Explanation

Value engineering analyzes the functions a project must perform and seeks alternative means to deliver them at the lowest total cost without sacrificing quality or required performance. It is a structured, team-based analysis rather than simple scope cutting.

Question 14Planning, Design, and Construction

A certificate of occupancy for a new health care building is issued by:

  1. the authority having jurisdiction after required inspections Correct answer.
  2. the architect of record upon substantial completion
  3. The Joint Commission after an accreditation survey
  4. the facility's property insurance carrier after a risk inspection

Explanation

The certificate of occupancy is a legal document issued by the local authority having jurisdiction once inspections confirm that the building complies with applicable codes. Accreditation, insurance, and architectural certification do not confer occupancy rights.

Question 15Planning, Design, and Construction

Which statement about temporary dust barriers in an existing hospital is correct?

  1. They may be installed across exit stairs to contain dust
  2. They eliminate the need for interim life safety measures
  3. They may replace fire-rated walls for the duration of the project
  4. They must not compromise existing fire-rated walls or smoke barriers Correct answer.

Explanation

Temporary barriers control dust and pressure but never substitute for required fire-resistive construction. Penetrations, door props, and attachments must not defeat the rating of walls, doors, or smoke barriers, and egress stairs must stay usable.

Question 16Planning, Design, and Construction

Functional performance testing during commissioning is intended to:

  1. verify that the contractor's O&M manuals have been delivered
  2. demonstrate that systems operate correctly under load and in all modes Correct answer.
  3. document the punch list of cosmetic defects
  4. confirm that equipment nameplates match the submitted submittals

Explanation

Functional performance testing dynamically operates systems through their sequences, modes, and load conditions to prove actual performance, not just documented specifications. Static checks and documentation reviews are prerequisites, not substitutes.

Question 17Planning, Design, and Construction

Before a newly installed medical gas piping system is placed into service, the system must be:

  1. approved by the installing contractor's foreman
  2. verified by an independent certified medical gas verifier Correct answer.
  3. purged with room air for 24 hours by the installer
  4. tested only for leaks at the outlets by clinical staff

Explanation

Medical gas systems require third-party verification by an independent, certified verifier who performs and documents the required tests and purity checks before the system is used for patient care. Verification independence keeps the installer from certifying its own work.

Question 18Planning, Design, and Construction

During a renovation of a hospital's main entrance, the project team must ensure that:

  1. alternate routes are provided only upon written request from a patient
  2. accessibility requirements are suspended until the project is complete
  3. an accessible route to the entrance and affected services is maintained Correct answer.
  4. accessible parking is temporarily eliminated to make room for equipment

Explanation

Accessibility requirements continue during construction: an accessible route of travel to the entrance, to altered areas, and to primary services must be maintained. Temporary disruption does not suspend the obligation to provide access.

Question 19Planning, Design, and Construction

When a contractor penetrates a two-hour fire-rated wall to install conduit, the penetration must be:

  1. protected with a listed firestop system tested to ASTM E814 Correct answer.
  2. covered with a metal plate on the finished side only
  3. left open temporarily to allow for additional cabling
  4. sealed with expanding foam insulation alone

Explanation

Penetrations of rated assemblies must be protected with a firestop system listed for that specific construction and tested to ASTM E814 (UL 1479). Approved systems restore the rating; improvised materials and one-sided cover plates do not.

Question 20Planning, Design, and Construction

Before a planned shutdown of an electrical branch circuit serving a nursing unit during construction, the facility manager should:

  1. perform the shutdown during shift change to reduce documentation
  2. proceed if the emergency generator is available as backup
  3. coordinate with clinical staff and confirm contingency plans Correct answer.
  4. notify only the contractor, who controls the schedule

Explanation

Utility shutdowns in patient care areas require advance coordination with clinical leadership, confirmation that critical equipment has temporary power or an acceptable workaround, and notification of all affected departments. The shutdown affects patient care, not just the construction schedule.

Question 21Planning, Design, and Construction

When several Life Safety Code deficiencies exist at the same time during a phased renovation, interim life safety measures should be:

  1. postponed until the construction project reaches substantial completion
  2. implemented only if the authority having jurisdiction issues a citation
  3. applied uniformly using a single standard measure facility-wide
  4. selected for each deficiency according to its impact on life safety Correct answer.

Explanation

ILSMs are risk-based: each deficiency is assessed for how it affects detection, suppression, containment, and egress, and compensatory measures are matched to that risk. A single blanket measure cannot fit every deficiency, and waiting for a citation or for completion leaves the hazard uncontrolled.

Question 22Planning, Design, and Construction

How does the owner's project requirements (OPR) document differ from the basis of design (BOD)?

  1. The OPR is a nonbinding wish list, while the BOD is a legal contract
  2. The OPR is issued after occupancy, while the BOD is issued before design begins
  3. The OPR states what the owner needs; the BOD describes how the design meets it Correct answer.
  4. The OPR is prepared by the contractor, while the BOD is prepared by the commissioning authority

Explanation

The OPR captures the owner's functional, operational, and performance expectations and is written early with owner input. The BOD is the design team's response, explaining the assumptions and approaches chosen to satisfy those requirements; commissioning tests performance against the OPR.

Question 23Planning, Design, and Construction

A temporary construction partition must be erected within a corridor that is a required means of egress. Which arrangement is acceptable?

  1. Rerouting occupants through the construction work area with a guide
  2. Reducing the corridor width below the minimum if a fire watch is posted
  3. Maintaining required egress width and keeping exits accessible Correct answer.
  4. Blocking one exit stairway because the other stairway remains open

Explanation

Work in a required means of egress must preserve the required width, keep exits reachable, and maintain any fire rating of the corridor. A fire watch does not compensate for lost egress capacity, and occupants must never be routed through a work zone.

Question 24Planning, Design, and Construction

A protective environment (PE) patient room is adjacent to a construction zone enclosed with a barrier. The correct pressure relationship is:

  1. PE room negative to the corridor; work area also negative to occupied space
  2. PE room and work area both maintained at neutral pressure to the corridor
  3. PE room positive to the corridor; work area negative to occupied space Correct answer.
  4. PE room negative to the corridor; work area positive to occupied space

Explanation

A protective environment requires the patient room to be positive relative to the corridor so unfiltered air does not enter. The construction enclosure is simultaneously made negative to surrounding occupied spaces so dust is contained and exhausted through HEPA filtration.

Question 25Planning, Design, and Construction

Before a newly constructed patient care unit accepts its first patients, which verification set is most complete?

  1. Certificate of occupancy, commissioning, and life safety testing Correct answer.
  2. Punch list completion, landscaping, and parking lot striping
  3. Final invoice, as-built drawings, and warranty binders
  4. Signed construction contract, furniture orders, and a marketing plan

Explanation

Occupancy readiness depends on legal permission to occupy, documented verification that safety-critical systems perform as intended, and accepted life safety system testing. Contract, marketing, cosmetic, and financial items do not establish that the unit is safe for patients.

Question 26Planning, Design, and Construction

When selecting a site for a new ambulatory care center, which factor is most important for the facility manager to verify early in planning?

  1. Proximity to competing hospitals
  2. Availability of tax abatements
  3. Utility capacity and emergency access Correct answer.
  4. Architectural style of adjacent buildings

Explanation

Early site evaluation must confirm that utilities, stormwater, and emergency vehicle access can support the intended clinical operations. Aesthetic and financial considerations are important but cannot overcome a site that cannot be served safely.

Question 27Planning, Design, and Construction

Schematic design drawings for a hospital addition are primarily intended to:

  1. Document as-built conditions at project closeout
  2. Serve as the contract documents for bidding
  3. Confirm scope, room relationships, and budget direction Correct answer.
  4. Establish final construction details and material specifications

Explanation

Schematic design translates the program into initial layouts and confirms scope and budget direction before detailed development. Construction details and bidding documents come later.

Question 28Planning, Design, and Construction

During design review, the facility manager's most useful contribution is to:

  1. Select the construction contractor
  2. Approve the architect's fee schedule
  3. Negotiate the land purchase
  4. Flag maintenance and life safety concerns Correct answer.

Explanation

The facility manager represents the ongoing operating and maintenance perspective during design. Catching access, cleaning, and life safety issues early avoids costly changes after occupancy.

Question 29Planning, Design, and Construction

In a traditional design-bid-build delivery, the owner holds separate contracts with:

  1. The architect and the construction manager at risk
  2. A single design-build entity
  3. The design professional and the general contractor Correct answer.
  4. The construction manager only

Explanation

In design-bid-build, the owner contracts separately with the design professional and the construction contractor. Design-build combines them under one entity.

Question 30Planning, Design, and Construction

To preserve independence, the commissioning authority for a new hospital project should:

  1. Be a member of the architect's design team throughout construction
  2. Report to the general contractor's project manager
  3. Be selected by the major equipment vendor
  4. Report to the owner, independent of the project team Correct answer.

Explanation

Commissioning independence prevents decisions from being biased by design or construction schedule pressures. The Cx authority should have direct access to the owner.

Question 31Planning, Design, and Construction

During construction, the facility manager's review of equipment submittals is most valuable for confirming:

  1. That the architect's invoice is accurate
  2. That equipment matches the hospital's parts and training Correct answer.
  3. That the project schedule has no float
  4. The contractor's markup percentage

Explanation

Submittal review lets operations staff confirm that equipment will fit existing maintenance programs, parts inventories, and staff training. It is not a financial or scheduling approval.

Question 32Planning, Design, and Construction

A construction phasing plan for work inside an operating hospital should primarily:

  1. Allow all areas to be renovated simultaneously
  2. Maximize the contractor's parking revenue
  3. Reduce the number of construction permits required
  4. Separate construction traffic from patient flow Correct answer.

Explanation

Phasing separates construction activities from clinical operations to protect patients and staff from noise, dust, and traffic. It is a patient-safety and operations tool, not a permitting or revenue tool.

Question 33Planning, Design, and Construction

When rainwater enters a construction area adjacent to patient rooms, the facility manager should first:

  1. Schedule a post-occupancy evaluation
  2. Isolate the area and dry it within 24 to 48 hours Correct answer.
  3. Cover the wet materials with plastic
  4. Wait for the area to dry naturally before resuming work

Explanation

Water intrusion creates conditions for mold growth, which can begin within 24 to 48 hours. The area should be isolated and dried promptly, with materials assessed for contamination.

Question 34Planning, Design, and Construction

When a construction project requires a fire alarm system to be out of service for several hours, the facility manager must ensure that:

  1. The alarm is silenced but no other action is needed
  2. The building is evacuated for the entire outage
  3. The contractor assumes all fire watch duties without documentation
  4. A fire watch and notifications are in place Correct answer.

Explanation

An impaired fire alarm system requires interim life safety measures, including a fire watch and notification of occupants and the fire department. The alarm cannot simply be silenced without compensatory action.

Question 35Planning, Design, and Construction

If construction will temporarily block a required exit corridor, the project team should:

  1. Implement interim life safety measures and alternate egress Correct answer.
  2. Reduce the occupant load of the building permanently
  3. Post a sign directing occupants to use a longer route
  4. Continue work and reopen the corridor at the end of the shift

Explanation

Blocking a required exit triggers interim life safety measures such as alternate egress, signage, and a fire watch. The corridor cannot be used as a construction zone without compensatory protection.

Question 36Planning, Design, and Construction

At project closeout, the systems manual provided by commissioning should include:

  1. Only the equipment warranties
  2. Operating procedures and maintenance requirements Correct answer.
  3. The contractor's bid documents and payment schedule
  4. The architect's marketing brochure

Explanation

The systems manual supports ongoing operation and maintenance after commissioning. It should include procedures, maintenance requirements, and training documentation.

Question 37Planning, Design, and Construction

A preconstruction risk assessment (PCRA) differs from an infection control risk assessment (ICRA) because the PCRA:

  1. Is completed after construction ends
  2. Focuses only on airborne pathogens and mold
  3. Replaces the need for an ICRA
  4. Addresses broader construction hazards, not just infection Correct answer.

Explanation

A PCRA takes a broad view of construction hazards, including life safety, utilities, noise, and access. An ICRA is specifically focused on infection transmission risk and does not replace the broader assessment.

Question 38Planning, Design, and Construction

During design review of a new patient care wing, the facility manager should verify that accessible routes:

  1. Link all public and staff areas without stairs Correct answer.
  2. May include steps if ramps are nearby
  3. Apply only to visitor areas
  4. Are provided only at the main entrance

Explanation

Accessible routes must provide a continuous path connecting public and staff areas without relying on stairs. Accessibility applies to both patient and staff spaces.

Question 39Planning, Design, and Construction

In a new hospital located in a high seismic zone, nonstructural components such as suspended ceilings and sprinkler piping must be:

  1. Installed without bracing to allow movement
  2. Omitted in patient care areas
  3. Supported only by the ceiling grid
  4. Braced and anchored to resist seismic forces Correct answer.

Explanation

In high seismic zones, nonstructural components must be braced and anchored so they do not fall or rupture during an earthquake. This protects occupants and keeps essential systems functioning.

Question 40Planning, Design, and Construction

When designing a behavioral health patient room, the facility manager should prioritize:

  1. Decorative glass mirrors and exposed plumbing
  2. Heavy furniture that cannot be moved
  3. Ligature-resistant fixtures and hardware Correct answer.
  4. Lockable patient-side storage for personal items

Explanation

Behavioral health rooms require ligature-resistant design to reduce self-harm risk. Fixtures, hardware, and furnishings should be selected for that purpose.

Question 41Operations and Maintenance

What is the primary purpose of a hospital's planned maintenance program for utility and equipment systems?

  1. To produce a written record that satisfies accreditation surveys
  2. To reduce unplanned failures and extend equipment life Correct answer.
  3. To replace the need for corrective maintenance entirely
  4. To shift all maintenance work to outside vendors

Explanation

Planned maintenance is scheduled work performed to keep equipment within design performance and to prevent deterioration that leads to breakdown. Documentation is a byproduct, not the goal, and no program eliminates corrective work completely. The value is measured in fewer failures, longer asset life, and safer systems.

Question 42Operations and Maintenance

A staff member reports sparking and smoke coming from an electrical panel in an occupied patient room. How should the facilities department classify the resulting work order?

  1. Deferred, pending a capital request for panel replacement
  2. Planned corrective work, to be scheduled during the next monthly PM window
  3. Emergency, requiring immediate response and isolation Correct answer.
  4. Routine, with completion targeted within 30 days

Explanation

Smoke or arcing at an electrical panel is an immediate fire and shock hazard in an occupied patient area, so it triggers the highest work order priority with an immediate response. Planned and deferred categories apply to conditions that pose no imminent risk. The panel must be de-energized and the area made safe before any follow-up repair planning.

Question 43Operations and Maintenance

According to NFPA 110, how is a Level 1 diesel emergency generator normally exercised each month?

  1. For 2 continuous hours at full nameplate rating
  2. At least 10 minutes with no load connected
  3. Only when a utility outage occurs
  4. At least 30 minutes under available load Correct answer.

Explanation

NFPA 110 requires monthly exercising of emergency power supply systems for a minimum of 30 minutes while carrying the load available at the time of the test. Running the set under load verifies that it can actually deliver power, not merely start. Longer full-load testing is a separate annual or periodic activity.

Question 44Operations and Maintenance

The Joint Commission requires fire drills in a hospital to be conducted at which frequency?

  1. Quarterly, on each shift Correct answer.
  2. Monthly, on the day shift only
  3. Annually, at the safety officer's discretion
  4. Semi-annually, on any shift

Explanation

Hospitals must conduct fire drills quarterly on each shift so that every shift demonstrates the ability to execute the fire response plan. Drilling each shift accounts for differences in staffing and supervision at night and on weekends. Monthly or annual drills do not meet the quarterly-per-shift requirement.

Question 45Operations and Maintenance

What is the required frequency for the visual inspection of portable fire extinguishers?

  1. Every three years, when hydrostatic testing is due
  2. Weekly, on each shift
  3. Monthly Correct answer.
  4. Annually, during the fire safety survey

Explanation

Portable extinguishers must be given a visual inspection at least monthly to confirm they are in place, accessible, and charged. Annual maintenance and hydrostatic testing at the interval stamped on the shell are separate requirements. Monthly checks catch tampering, damage, and pressure loss between annual services.

Question 46Operations and Maintenance

Which NFPA document contains the requirements for medical gas and vacuum systems in health care facilities?

  1. NFPA 99 Correct answer.
  2. NFPA 25
  3. NFPA 70
  4. NFPA 101

Explanation

NFPA 99, the Health Care Facilities Code, governs medical gas and vacuum system design, installation, testing, and maintenance. NFPA 70 covers electrical installations and NFPA 101 covers life safety features. NFPA 25 addresses inspection and testing of water-based fire protection systems.

Question 47Operations and Maintenance

Which item is the best candidate for stocking as a critical spare part?

  1. An extra waiting room chair kept for furniture replacement
  2. A control board for the sole OR air handler Correct answer.
  3. A replacement filter for a non-critical exhaust fan in storage
  4. A decorative light fixture used in the main lobby area

Explanation

Critical spares are parts whose absence would immediately disrupt patient care or force a service outage. A control board for the only air handler serving operating rooms meets that test because there is no backup and the clinical impact is immediate. Spares for cosmetic or redundant equipment tie up capital without protecting operations.

Question 48Operations and Maintenance

A facility scheduled 240 planned maintenance work orders last quarter and completed 216 of them on time. What is the PM completion rate?

  1. 80 percent
  2. 90 percent Correct answer.
  3. 24 percent
  4. 96 percent

Explanation

PM completion rate equals completed scheduled work orders divided by total scheduled work orders, multiplied by 100. Dividing 216 by 240 gives 0.90, or 90 percent. This measure shows whether the planned maintenance program is actually being executed as designed.

Question 49Operations and Maintenance

An operating room uses an isolated power system. How often must the line isolation monitor be tested?

  1. Daily
  2. Quarterly
  3. Monthly Correct answer.
  4. Annually

Explanation

NFPA 99 requires the line isolation monitor in an isolated power system to be tested monthly to confirm that it detects and alarms on hazardous leakage current. The monitor is a safety device, so a silent failure would leave staff unaware of a fault. Annual or quarterly intervals are too infrequent for a life-safety alarm function.

Question 50Operations and Maintenance

Per ASHRAE Standard 170, what is the minimum total air change rate for an operating room?

  1. 20 total air changes per hour Correct answer.
  2. 12 total air changes per hour
  3. 6 total air changes per hour
  4. 25 total air changes per hour

Explanation

ASHRAE 170 sets the operating room minimum at 20 total air changes per hour, of which at least 4 must be outdoor air. The high air change rate dilutes airborne contaminants and supports the positive pressure relationship. Lower rates apply to less critical spaces such as patient rooms.