The COVID-19 pandemic took us all by surprise this year. It has affected everyone and every business. A very large portion of manufacturing was shut down in an effort to “flatten the curve,” and even those who remained open have dealt with COVID issues such as employees who are afraid to come to work for fear of being exposed. And those who are working do so under social-distancing guidelines that create difficult conditions. All of this makes the issue of quality – the quality of our products and the quality of our lives – more significant.
There is a good chance that you have been wearing a mask to help reduce the spread of COVID-19. We have come to understand that N95 masks are much more effective than simple cloth masks, but something is better than nothing. So N95 masks are recommended for health-care professionals, and nearly everyone else should simply wear a cloth mask to help reduce the spread of the virus.
What about “fever screening?” It is in the news constantly. Airlines, casinos, hospitals, office buildings and many manufacturing facilities are doing this. But what, exactly, are they doing? What is fever screening? Doesn’t it simply mean that someone checks your temperature to be sure you don’t have a fever?
Actually, no! It turns out that fever screening and checking your body temperature to determine if you have a fever are two entirely different processes. In the simplest form, fever screening is an act parallel to mom touching your forehead to see if you are warm. This is screening: the process of identifying those who are suspect of having an elevated body temperature. And it is essential to understand that this is not “Fever Screening.” This is the process of observing whether one has an elevated skin temperature.
Fever Screening and Skin Temperature
Having determined that you feel a little warm – that is to say, having been screened and found to exhibit an elevated skin temperature (EST) – a medical procedure is then performed to assess whether you have a fever. Your temperature is measured using a clinical contact thermometer. A measurement of approximately 98.6°F is considered normal body temperature. A body temperature of 100.4°F or more is considered to be feverish.
One would think that the infrared temperature sensor is measuring your body temperature when you are screened, right? Wrong! There are two infrared techniques in use for detecting an elevated skin temperature. One is measuring the forehead temperature, and the other is measuring the tear duct (medial canthus) temperature. But neither of these correlates directly with the core body temperature.
In the words of the U.S. Food and Drug Administration (FDA), if you want to detect elevated skin temperatures properly, you should comply with ISO TR 13154, Medical Electrical Equipment – Deployment, Implementation and Operational Guidelines for Identifying Febrile Humans Using a Screening Thermograph.
Since the federal government has declared an official state of national emergency due to the pandemic, however, the FDA has suspended their rules and issued specific guidance on fever screening (a media term) in a letter to the public dated April 2020.
Fever Screening or Elevated Skin Temperature?
What is the big deal between one or the other? The FDA, in fact, considers it a very big deal. It is an FDA violation for a company to market a piece of equipment and state that it is for “Fever Screening.” The equipment may only be referred to as an elevated skin-temperature measurement system, and even this requires approval by the FDA along with testing and an FDA 510(k) approval. Keep in mind that as soon as the “national emergency” is rescinded, the rules will be enforced.
Fundamentally, the issues of fever screening and elevated skin temperatures directly parallel our industrial applications. In many forging applications, for example, metal billets pass through an induction heater to achieve the proper temperature for forging. In forging, temperature is the primary factor for determining product quality. The typical forging line is set up with an infrared temperature sensor to essentially screen the temperature of each billet as it emerges from the induction heater.
The goal is to achieve a specific billet core soak temperature for forging. But the infrared sensor only gets the external skin temperature as it emerges from the heater. Billets are rejected if they are either too hot or too cold. It is really no different when we are checking for elevated skin temperatures on people.
What exactly does the FDA recommend?
The FDA recognizes the use of infrared cameras to observe the temperature of the tear duct (medial canthus) and compare this measurement with a blackbody source in the field of view as the only valid technique for screening for elevated skin temperature. Valid refers to a technique that has FDA 510(k) approval for elevated skin-temperature measurement as adjunctive diagnostic screening devices. The FDA also currently permits non-contact infrared thermometers as an emergency triage measure for adjunctive diagnostic screening. In both cases adjunctive means that it is mandatory to use a clinical contact thermometer to verify the results of all subjects found to have an elevated skin temperature (EST).
The fundamental FDA guidelines for EST fever screening using infrared are:
- Screen one person at a time.
- Measure the tear-duct temperature.
- Compare the tear-duct measurement with a blackbody source in the field of view.
- If the observed temperature equals or exceeds 100.4°F, then validate the result.
- Measure the temperature of the suspected elevated temperature using a clinically approved contact thermometer.
What about using handheld infrared temperature sensors to measure the forehead, like we see in the media? The official guidance is the same, but the process requires additional steps for a quality result.
More about Forehead Temperatures
The temperature measurement of the forehead can represent an approximation of the body temperature, but it can also vary by several degrees.
Let’s explore to understand what is happening. When you are sitting in a stable, controlled environment (68-75˚F), the forehead skin temperature may typically measure about 97˚F, or approximately 1.6˚F below the core body temperature. The fever threshold is 100.4˚F based on a reference point of 98.6˚F. If we are measuring foreheads and the average forehead is 97˚F, then our fever threshold should be 100.4˚-1.6˚, or 98.8˚F.
But if the people being screened just parked their car and walked across the lot and it is 50˚F outside, then their average forehead skin temperature will be much lower than 97˚F. The proper technique is to have them sit in the screening area for a period to allow their forehead temperature to acclimate. Without allowing time to acclimate, the forehead temperature will certainly vary, and the result of forehead temperature screening measurements are meaningless.
An example from the forge shop is similar. It is all about quality. As a billet emerges from the induction heater, the skin is at its peak temperature. In fact, it is common for a billet to be rejected as being too hot due to the billet having a sharp edge from being cut. This sharp edge can become much hotter than the body of the billet. If the temperature sensor sees it, it is rejected as being too hot. Actually, if given just a few seconds to exit the heater, the temperature measurement would be a more accurate measurement of the billet temperature.
Beware of False Negatives
When performing EST tests with people, the result of a false-positive measurement is that the subject has their actual temperature measured with a clinical thermometer. But the result of a false negative measurement means that you are providing entry to a person who is actually exhibiting a symptom of illness. Just as with heated forging billets, it is all about quality. The purpose of screening for elevated skin temperature is to identify those persons who are truly symptomatic (feverish).
Fever screening can be effective at slowing the spread of COVID-19 because it can correctly identify those who are symptomatic – but only when it is done properly. And, as in manufacturing, we know that quality relies on properly trained and skilled personnel.
The American Academy of Thermology (AAT) is an organization of medical professionals whose specialty is the study of the thermal characteristics of the human body. They have developed guidelines and training for the public for implementing effective elevated skin-temperature screening (fever screening) techniques, which comply with guidance from the FDA. In addition to the guidelines, the AAT has developed free online training to teach your company’s health personnel the proper way to implement fever screening for your employees.