Instead of addressing Bair Hugger’s safety issues, 3M has resorted to personal attacks on respected researchers, top-tier journals and Dr. Augustine to distract from the real issues. Meanwhile, the false forced-air warming (FAW) safety claims continue to directly endanger patients undergoing joint replacement surgery.

click for a condensed PDF summary



“Commercially driven junk science that has no basis in reality whatsoever.”1

REAL FAW FACT: The characterization of “junk science” is a construct from the 3M marketing department. Why? Because they have no science showing that forced-air warming (FAW) is safe in orthopedic implant surgery.

How can 3M characterize peer-reviewed studies published in top-tier medical journals (eg. Anesthesia & Analgesia, Journal of Bone and Joint Surgery), as “junk science?” 3M doesn’t like the findings, but that does not turn peer-reviewed studies by respected researchers into “junk science.”

We encourage you to evaluate the studies yourself: Research Comparison.


More than 170 studies and 60 randomized controlled trials show the safety and effectiveness of this system.”
-3M’s marketing piece, “Let’s spread good science.”

REAL FAW FACT: 3M fails to mention that not one of these studies applies to peri-prosthetic joint infections—the subject of more than 800 lawsuits in Federal Courts around the country. Click here to read aonal airflow: “If airflow is interrupted, rapid air turbulence can stir settled particles, enabling them to become airborne thus increasing the risk for wound contamination.”10

Like all heat, 3M’s heat also rises. Waste heat from FAW disrupts laminar flow and should be contraindicated in contamination-sensitive surgeries, where a single bacterium can cause a catastrophic infection.


“Numerous studies have indicated that patients warmed with forced air have a reduced risk of SSI because it is so effective at preventing hypothermia.”

REAL FAW FACT: The oft-referenced Kurz study involved colorectal resection surgery and showed that normothermic patients are less likely to develop infections and have shorter hospital stays.2 True—but only for soft-tissue surgeries.

3M obviously knows the difference between soft-tissue surgical site infections (SSI) and peri-prosthetic joint infections (PJI), but they intentionally blur the two in marketing communications. The mechanism for infection is completely different for SSIs and PJIs. The implantation of foreign material in the body fundamentally changes the infectious process. An inoculum of more than one million bacteria is required to cause a soft-tissue SSI, and the bacteria usually enter the wound from the adjacent skin or cut bowel.35 In sharp contrast, a single bacterium can cause a PJI, and it usually enters the wound as airborne contamination.18, 25, 36


“Published studies have demonstrated that the use of forced-air warming does not increase either the risk of wound contamination, or bacterial contamination of the operating room.2,3. When tested during actual surgical conditions, forced-air warming was shown to decrease the bacterial count at the surgical site.”4-6

REAL FAW FACT: Citing research conducted on conscious volunteers lying on an operating table as an example of a study done in “actual surgical conditions” is simply false.

The small sample sizes involved in this research, combined with the unpredictability of culture plate studies, makes these statements unfounded.

Click here to read further examination of the cited studies.


“Moretti’s study of 30 patients undergoing hip implantations indicates that Bair Hugger therapy does not pose a risk for hospital-acquired infections. Not a single patient who participated in the study suffered a hospital-acquired infection.”
-3M’s marketing piece, “Let’s spread good science.”

REAL FAW FACT: This analysis of the Moretti research directly contradicts the results of an independent review article of the very same study in The Journal of Hospital Infection which states, “Moretti et al. found an increased bacterial load at the surgical site when FAW was used.”7 With a sample size of 30 patients, for just one patient to acquire a PJI, the infection ratio would have to be over 3%, compared to the national average of 1.27%, for hip replacements.

An increase in bacteria leads to an increased risk of infection.8 Since Moretti found an increase in bacteria near the surgical site when FAW was used, 3M’s conclusion is illogical: more bacteria always increase the risk of infection.


3M insists the excess heat produced by Bair Hugger defies the laws of physics, claiming it “quickly dissipates” in the OR, and it could not possibly rise because it comprises “less than one percent of the airflow” in the OR. They also fervently deny the existence of waste hot air convection currents.
-3M’s marketing piece, “Let’s spread good science.”

REAL FAW FACT: Only about 15% of the 1000 watts of heat produced by the Bair Hugger blower is actually transferred to the patient9. The excess heat then escapes into the OR and mobilizes contaminants. Click here to see videos and studies showing the three ways that FAW waste heat contributes to surgical site contamination.

Airflow obstructions, such as clinicians and surgical lights, create “dead zones” that are shielded from the ventilation airflow. Watch how FAW waste heat easily defeats the protection of the laminar ventilation system, carrying contaminated air from the floor into the dead zones, and then into the surgical field.

The following quote from the APIC Guide to the Elimination of Orthopedic Surgical Site Infections further emphasizes how critical it is to maintain unidirectional airflow: “If airflow is interrupted, rapid air turbulence can stir settled particles, enabling them to become airborne thus increasing the risk of wound contamination.” (Greene 2010)


“None of the articles cited to support this false claim actually conclude that the Bair Hugger system or forced-air warming causes an increased risk in orthopedic infections.”
-3M’s marketing piece, “Let’s spread good science.”

REAL FAW FACT: Multiple studies show an increase in the level of airborne contamination; one links FAW to higher infection rates.11

Reason demands one to conclude that waste heat from Bair Hugger increases the risk of PJIs. If bacteria increases risk of infection and FAW increases bacteria, then FAW increases risk of infection. Mathematically: if A=B and B=C, then A=C.

A. Waste heat from FAW rises, mobilizing infectious contaminates from the floor up into the sterile surgical field.11-15 Five published studies have found this to be true.

B. The risk of developing a PJI is directly related to the amount of contamination in the air. The concentration of airborne contaminates correlates directly with the concentration of contaminates in the wound.8, 16-24 The concentration of contaminates in the wound correlates with the risk of PJIs, as PJIs can develop from just one bacterium.18, 20, 25

C. FAW waste heat, therefore, increases the risk of acquiring an orthopedic infection.


“All the papers that Augustine Temperature Management cites were written by Augustine employees or consultants.”1

REAL FAW FACT: Wrong. Three of the studies were completely unrelated to ATM, and ATM’s minimal involvement in the other three is clearly disclosed. All prove that waste heat from FAW mobilizes contaminates from the floor, up and into the sterile field.

On the contrary, 3M frequently cites materials produced by paid consultants, including:

>A “white paper”, which was not peer-reviewed or published in any scientific journal, written by Dr. Javad Parvizi, a member of the Scientific Advisory Board of 3M’s Infection Prevention Division and paid consultant of 3M.

>A deceptive study by Dr. Daniel Sessler,26 the design of which was so deeply flawed that it should be labeled “research fraud.” Read a detailed critique of this study and its dishonest design here.


“In addition, thorough examination by multiple sources has conclusively determined there is no significant disruption of laminar airflow tied to the use of forced-air warming units.”

“One study conducted to address airborne contaminant and ventilation flow questions found that convective warming had no negative effects on air quality in the operating room…”

REAL FAW FACT: Attempting to distract from the truth, 3M continually cites statements from flawed studies produced by paid consultants. This Research Comparison shows that none of the studies 3M references actually addresses the issue—the issue raised by more than 800 lawsuits. Sessler’s 3M-designed waste heat study is so deceptive that Dr. Augustine has called it “academic misconduct.” Read Dr. Augustine’s full critique of the study.


3M frequently cites to ECRI’s analysis as proof that Bair Hugger is safe.

ECRI found disruption of OR ventilation airflow to be “particularly worrisome” in orthopedics; however, since a prospective, randomized controlled trial has not been conducted, ECRI determined that there isn’t conclusive evidence to make a recommendation either way. They did commit to update their recommendations as additional information becomes available.

ECRI recently conducted a comparative evaluation of the safety, effectiveness and cost of HotDog patient warming. ECRI subscribers can access it on their website. Email to request a printed copy.


“Bair Hugger warming units provide a second level of filtration. Operating room air is already filtered, and the Bair Hugger unit filters inlet air again with a high efficiency 0.2 micron filter.”

REAL FAW FACT: 3M represented to the FDA that Bair Huggers have HEPA filters. They don’t. Research showed that the Model 750 filters that were purported to be HEPA quality were in fact only 63.8% efficient.27

Similar research published in APIC’s journal reported that the 0.2 micron filters on the Model 505 blowers had been reduced from 93.8% efficiency to 61.3%.28

In the same study, micro-organisms were cultured from the internal air-flow paths of 92.3% of forced-air blowers. 58% of the blowers tested were found to be internally generating and emitting significant levels of airborne contaminants larger than 0.3 microns in size (germ size), up to 35,272 particles per ft3 of air (80 million particles per hour).

Micro-organisms were cultured from the internal air-flow paths of 100% of forced-air blowers tested in a study by Reed.29 100% of the blowers were emitting internally generated particles greater than 0.3 microns in size, up to 112,000 particles per ft3 of air (300 million particles per hour). Emitted particle count was 40 times greater than the intake particle count for that blower, and virtually all of the emitted particles were internally generated.


“Because Bair Hugger blankets are single use, they cannot transmit infection from one patient to another.”

REAL FAW FACT: The risk of cross-contamination isn’t about Bair Hugger blankets.

FAW is only partially disposable. The blower and hose are used on thousands of different patients, sometimes moving from one OR to another. One published study showed that 92% of FAW blowers are contaminated with bacteria, and 58% internally generated and emitted germ-sized particles.28 The contamination is significant because high-velocity air blows across the germ colonies. The contaminated hot air vents under the drapes, mixes with “dirty” floor air and rises into the sterile field.

Using Bair Hugger on a patient with an infection like MRSA is unwise and unsafe. Blowing air over the skin of a patient with MRSA can actually aerosolize the germs, exposing other patients and clinicians to increased risk of infection.30

In other marketing pieces, 3M wants to lead you to believe that there is a high cross-contamination risk with HotDog. The CDC considers HotDog blankets “noncritical items”, like blood pressure cuffs or crutches. According to the Guideline for Disinfection and Sterilization in Healthcare Facilities, “Virtually no risk has been documented for transmission of infectious agents to patients through noncritical items.” 31, 32

Contaminated patient care equipment is the least-frequently cited source of infectious agents causing HAI.33 Read more infection control information here.


“Conductive warming methods do not come into contact with enough body surface area to warm a patient as effectively as a convective warming method (15%–21% vs. 64%, respectively).”
-3M’s marketing piece, “Let’s spread good science.”

REAL FAW FACT: The studies cited in this statement were not conducted using HotDog. We agree that surface area is the key to effectiveness. In fact, HotDog is the only system that can warm from above and below simultaneously. The HotDog underbody mattress overlay is completely flexible, unlike the water systems or stiff underbody heaters that were used in the studies cited.

A recent study found HotDog warms significantly faster than forced-air because, the researchers noted, it covers a “larger surface area” and transfers heat more efficiently.34

“Conductive technology takes two to three times longer to rewarm patients than convective warming.”
-3M’s marketing piece, “Let’s spread good science.”

REAL FAW FACT: This study was done using the first prototype HotDog blanket that was never released for sale in the United States. At least one of the authors was a paid consultant to 3M and the study was intentionally designed for forced-air to win. HotDog’s current design is more effective than forced-air.

Recent research found that HotDog showed significantly higher warming rates than FAW (0.35° C/hour versus 0.02° C/hour). The authors’ conclusion: “We conclude from these data that the clinical heat transfer effectiveness of [HotDog warming] is significantly greater than FAW convection. This is due to the combination of conductive heat transfer and the larger surface area of simultaneously heating from above and below the patient.”34

We encourage you to conduct temperature audits to see for yourself how effective HotDog really is. Click here to learn more about effectiveness.


3M Bair Hugger Safety Study Intentionally Deceptive – Read Why

Read Dr. Augustine’s full critique of the study here

Link to Dr. Augustine’s full critique of 3M’s Sessler/Olmstead study (citation 26 below)

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