Cold on shift: a clinician's guide to thermal comfort in hospitals
Operating rooms are designed to run between 68°F and 75°F (20°C to 24°C), and many sit near the cool end to protect gowned surgeons and control humidity. That leaves circulating nurses, anesthesia staff and other less active team members cold. The practical answer is layered, policy-compliant attire: a clean warm-up jacket, a low-lint under layer and added core warmth, all within your facility's attire and device rules.
Why are operating rooms and hospitals kept so cold?
Operating room climate is set by engineering standards, not by staff preference. ASHRAE Standard 170-2008, the ventilation standard for health care facilities, specifies a design range of 68°F to 75°F and 30% to 60% relative humidity for operating rooms. A 2010 addendum lowered the humidity floor to 20%, and in 2013 the Centers for Medicare and Medicaid Services (CMS) issued a categorical waiver allowing hospitals to operate anesthetizing locations at that lower humidity level.
Within that band, many rooms run cool. A 2023 randomized trial of surgeon cooling vests describes operating rooms maintained near 20°C (68°F), and a 2026 German study measured 20.1°C to 20.7°C in a working operating room with unidirectional airflow. CMS also notes that each operating room should have its own temperature control, which is why one room can feel very different from the next.
The reasons are practical. Surgeons work under insulating gowns and bright lights, humidity must be controlled, and cooler air helps the scrubbed team stay comfortable during long cases. The people who are not scrubbed pay the thermal price.
Who gets cold in the OR, and who overheats?
Thermal comfort depends on metabolic rate, clothing and air movement, so a single room temperature cannot suit everyone. A 2026 model-based study in Atmosphere applied the ISO 7730 comfort method to one operating room at 20.5°C. It predicted that 75% of male surgeons wearing 7.5 kg lead aprons would be dissatisfied from heat, while 22% of female anesthesiologists would be dissatisfied from cold. The authors concluded that no uniform environment can satisfy every professional group.
Field data point the same way, with nuance. A 2025 survey of 254 operating room staff across 19 hospitals in Nanjing, China, found that surgeons tended to feel too warm and anesthesiologists tended to feel cold, while circulating nurses in that sample reported the highest comfort. An earlier Belgian study in Building and Environment found that technical standards could not produce acceptable conditions for every team member and noted that nurses' cold sensations could be improved with longer-sleeved clothing.
The popular summary, surgeons hot and nurses cold, is directionally right but incomplete. Who is cold depends on the room, the case, the role and the clothing each person is allowed to wear.
What does AORN guidance allow for warm layers?
The Association of periOperative Registered Nurses (AORN) Guideline for Surgical Attire is the reference most US facilities build their policies on. AORN's 2024 summary describes surgical attire as a scrub top, pants or dress, with or without a long-sleeve scrub jacket, also called a warm-up jacket, and says the team should decide which types of fabric may be worn and how much may extend beyond the surgical attire.
The 2019 edition made several points that still shape policy. Arms may be covered during preoperative patient skin antisepsis, but no recommendation was made for long sleeves at other times. No recommendation was made on personal clothing under scrubs; instead, facilities should set policies on fabric type, laundering frequency and laundering method. Scrub attire should be laundered at a health care-accredited laundry facility, according to state requirements, or according to CDC recommendations, and fabrics should be tightly woven and low linting.
AORN updated the guideline again in 2025, reinforcing that scrubs or personal clothing contaminated with blood or body fluids must be removed and left at the facility for laundering. Because editions change, always check your facility's current policy rather than relying on memory.
How can clinicians stay warm on shift?
Warmth in a cold clinical area comes from the same principles as any cold environment, adapted to infection-control rules. OSHA's cold stress guidance recommends layers: a moisture-wicking inner layer, an insulating middle layer and an outer layer, and it notes that the body shifts blood flow from the hands and feet toward the core as it cools.
In practice, that translates into a short checklist that fits most attire policies.
Start with a close-fitting, low-lint base layer that your policy permits under scrubs.
Keep a clean, facility-laundered warm-up jacket for times when arms may be covered.
Add core warmth with a thin vest or insulated layer, since a warm core supports warmer hands.
Keep feet and head covered with approved socks, shoes and head coverings.
Move when you can, eat and hydrate, and ask whether room temperature can be adjusted between cases.
Can you wear a heated or thermal vest under scrubs?
Many facilities allow a thin vest under or over scrubs, but the answer depends on local policy for personal clothing, fabric type and laundering. Passive options include insulated and heat-reflective vests. Active options include vests with pockets for air-activated warmers or battery-powered heating inserts. Battery devices raise separate questions in clinical areas, particularly near the oxygen-enriched environments found in operating rooms.
Purpose-built staff warming has a short history. In 2016, Augustine Temperature Management introduced a Clinician Warming Vest that used a conductive polymer heating insert connected by cable to the company's HotDog controller at low voltage. HEATJAC, founded by an anesthesiologist, designed its low-profile thermal platform to be worn under or over scrubs, with pockets that accept warming inserts; as with any garment, staff should follow their facility's attire and device policies.
Does cold affect clinical performance?
Cold hands are more than a comfort issue. A widely cited 1995 review in Applied Ergonomics identified a local skin temperature of 15°C, a nerve temperature of 20°C and a muscle temperature of 28°C as minimum criteria for hand function, and summarized the evidence simply: cold means loss of dexterity.
A 2025 exploratory study found that dexterity losses could begin at finger skin temperatures near 23°C, and that brief whole-body rewarming shifted those thresholds. A 2024 randomized crossover study at 5°C found that heating the hands kept fingers warmer and improved pegboard times by 14.5%. Operating rooms are far warmer than 5°C, so these findings describe mechanisms rather than predict OR outcomes, but they explain why cold staff often notice clumsier hands.
Where else in the hospital do staff get cold?
Cold exposure extends well beyond the operating room. Staff work in cooled interventional suites, sterile compounding cleanrooms, laboratories, specimen and blood storage areas, decedent care rooms and loading docks. CDC's vaccine storage toolkit sets refrigerator storage at 2°C to 8°C (36°F to 46°F) and freezer storage at -50°C to -15°C, so anyone who works in or near walk-in units spends time in genuinely cold air.
The same layering principles apply, adjusted for each area's garbing rules. Sterile compounding, for example, follows USP General Chapter 797, which governs personnel garbing and facility conditions.
What about staff who overheat?
The opposite problem is real, especially for surgeons under gowns and lead aprons. In a 2023 randomized crossover trial of 30 orthopedic surgeons across 120 operations, an ice-pack cooling vest reduced thermal discomfort by 2.1 points on a 10-point scale and lowered perceived sweating and fatigue, without measurable changes in core temperature or cognitive test scores.
Cooling for surgeons and warmth for the rest of the team are two halves of the same design problem. Role-specific clothing often does more than a thermostat fight.
Quick reference: roles, typical experience and practical options
The table summarizes common patterns reported in the studies above. Individual experience varies with the room, the case and personal factors.
| Role | Typical thermal experience | Practical options within policy |
|---|---|---|
| Scrubbed surgeon | Often too warm under gown, lights and lead | Cooling vest under gown, lighter under layers |
| Anesthesia clinician | Often cold; low activity near supply airflow | Warm-up jacket, core vest, warm under layer |
| Circulating nurse | Varies; cold between tasks is common | Warm-up jacket, thin vest, movement |
| Surgical technologist (scrubbed) | Often comfortable to warm | Breathable under layer |
| Pharmacy, lab and storage staff | Cold in cleanrooms and cold rooms | Layering per area garbing rules |
Key takeaways
Operating rooms are designed for 68°F to 75°F, and many run near 20°C, which favors gowned surgeons over less active staff.
Research consistently shows that no single room temperature can satisfy every surgical role.
AORN guidance recognizes warm-up jackets and leaves personal under layers to facility policy, with strict laundering rules.
Core warmth, low-lint layers and policy-approved vests are the most practical tools for cold staff.
Anyone with persistent cold hands, color changes or numbness should talk to a clinician about symptoms.
Frequently asked questions
What temperature are operating rooms kept at?
ASHRAE Standard 170-2008 specifies a design range of 68°F to 75°F (20°C to 24°C) for operating rooms. Many rooms run near the cool end of that range, around 20°C, and each room can usually be adjusted separately.
Why are operating rooms so cold for nurses?
Room settings are chosen partly for gowned surgeons working under lights, who produce and trap more heat. Circulating and anesthesia staff move less during parts of a case and wear lighter clothing, so the same air feels colder to them.
Can I wear a jacket over my scrubs in the OR?
AORN recognizes a long-sleeve scrub jacket, also called a warm-up jacket, as part of surgical attire. Most facilities require it to be clean and laundered according to policy, so check your local rules before wearing a personal jacket.
Can nurses wear a heated vest under scrubs?
It depends on your facility's policy for personal clothing, fabric and electrical devices. Passive vests and air-activated warmers raise fewer questions than battery devices, which may need approval in some clinical areas.
Does being cold affect surgical dexterity?
Research shows that cooling of the hands reduces dexterity, with a classic threshold near 15°C finger skin temperature and newer evidence of earlier effects. Scrubbed surgeons are rarely that cold, but staff with exposed hands in cold rooms may notice changes.
What should I do if my hands turn white or blue in the cold?
Color changes, numbness or pain in the fingers can have several causes, including Raynaud's phenomenon. Talk to a clinician about these symptoms rather than managing them with warm layers alone.
Related reading
thermal gear for anesthesia providers: what works at the head of the bed
warm layers for dentists, hygienists and assistants: a buying guide
how to get a thermal vest approved for use in the OR or clinical areas
Sources
Environmental Conditions for Operating Rooms (ASHRAE Standard 170-2008 summary), Barton Associates
Relative Humidity in Anesthetizing Locations, S&C 13-25, Centers for Medicare and Medicaid Services
One Operating Room, Two Thermal Worlds: Determinants and Limits of Thermal Comfort for Surgical Staff, Atmosphere (MDPI), 2026
Field questionnaire survey on thermal comfort of medical personnel in operating rooms for hospitals in Nanjing, Energy and Buildings, 2025
Surgical Attire, Stethoscopes and Personal Items, AORN Periop Today
Cooling vest improves surgeons' thermal comfort without affecting cognitive performance: a randomised cross-over trial, Occupational and Environmental Medicine, 2023 (PMC)
Physiological criteria for functioning of hands in the cold: a review, Applied Ergonomics, 1995
About HEATJAC. HEATJAC is a thermal architecture company founded by an anesthesiologist. We design patented garment systems that capture, conduct and broaden warmth across the body, and we publish this knowledge hub because the science of staying warm should be public. HEATJAC products are not medical devices and are not intended to diagnose, treat, cure or prevent any disease.