No marketing material about Infrared heating (near, medium or far) seems complete without a statement of the “wonderful health benefits” of the technology.
Pandora’s box – it seems – was opened just a crack, allowing very clear and specific medical uses of certain types of infrared in very specific, tightly controlled ways, to become a general miracle technology available to all – if you believe the claims. The hype does not help the market or the consumer.We would like to put the record straight.
The highly transmissive properties of Near Infrared and its intense heat lend it particular medical benefits when dealing with certain skin and neurological conditions. The high intensity heat and greater transmissiveness of Near IR through the skin imply carefully controlled exposures targeting only the required skin area, when used by a qualified medical practitioner.
It is too general to say that exposure to Near Infrared as a rule is “good for the skin and muscles” – a statement we have seen describing generally available Near Infrared lamps.
Uncontrolled, frequent or long-term exposure to Near Infrared can cause thermal burns and ageing effects such as “Bakers Arms” or “Glassblowers Face” (Cho & others, 2009). Eye damage can also occur because Near Infrared transmits as far as the cornea – implying time limits or goggles should be employed when eye contact is likely (Voke 1999). The colour of the Near IR light itself is not relevant to its effects (ICNIRP 2006) as we have also heard statements like “it doesn’t affect horses, because they can’t see red”.
No infrared wavelength penetrates into muscle, so any such claim for Near Infrared is false and although Near Infrared lamps are light emitting and radiant “like the sun”, the Infrared has no known capability to help Vitamin D absorption (which we have also seen claimed, but is a property of UVB, not Infrared).
Reducing the wattage; reducing the voltage into the bulb or just moving the lamp further away does does not make Near IR “safer” per se, it just reduces the peak intensity of the lamp to a point where the wavelengths will be in the Medium to Far Infrared bands and the physical properties claimed as being “Near IR” no longer relevant anyway. We have seen a number of Near Infrared heater dealerships selling their lamps with dimmer switches and still claiming the “medical” benefits of Near Infrared.
The particular medical applications of Near Infrared are not generalisable for Medium and Far infrared, which is another common error. Whilst this may make Medium and Far Infrared appear less exciting to a marketer, it does at least also mean Medium and Far Infrared don’t have the same safety issues of Near Infrared either.
But the truth is perhaps more exciting than the fiction anyway.
Medium and Far Infrared are not as transmissive as Near Infrared (don’t penetrate as deep), but are far better absorbed by the skin. This better absorption is primarily due to the 80 percent water content of skin. Water absorbs heat specifically well at 3 microns (the start of Far Infrared) and throughout the Far Infrared band. More general warming therefore ensues because of conduction through skin tissue and convection through capillaries, leading – as the ICNIRP itself recognises – to a greater overall increase in body temperature than is possible via the more intense-but-local effect of Near IR.
This effect of Far Infrared is therefore biologically significant to human and animal skin and gives Far Infrared all sorts of advantages in terms of energy efficiency and comfort versus more powerful, hotter Near and Medium IR competitors. This is the message that marketers should really be pushing.
It is wrong to claim this effect as medically biologically altering in some way, instead of just comforting. We all like being warm and we feel a sense of wellness in a comfortable environment. An absence of cold and damp are also helpful in maintaining health and recovery from illness. But to suggest the Far Infrared is doing something additional to our biology in the process is not yet proven by science – but it certainly also isn’t doing any harm either (ICNIRP 2006).
On a final note, just as Near IR sellers dim their lamps and claim Near IR medical benefits whilst mainly emitting Medium/Far Infrared, we have also seen other Near IR sellers – perhaps aware of the potential harm caused by exposure to Near IR – claiming they are Far Infrared (and still claiming all those Near IR medical benefits too). It is true that part of the spectral output of the Near IR bulbs occurs in the Far IR wavelengths but that doesn’t make them Far IR. The clue is in the light – which means it has to be Near, or Near/Medium IR. The Far IR output of these lamps is actually weaker than it would be with an emitter optimised to peak in the Far IR wavelengths in the first place.
Conclusions:
The truth has run away with the marketing at present. The UK Health and Safety governing body for example has no guidelines on the subject, other than “reasonable precautions” and otherwise points to the ICNIRP as the ultimate authority in this respect who come down more definitively about Near IR, but fall short of stating guidelines of distance, time or intensity in its use.
The sensible approach is this:
Near IR is suitable for environmental temperature control, where any animal skin and eye contact is either not envisaged, not direct, adequately protected or easily avoided. Where Near IR is being “stepped-down” either electronically or by distance in order to provide Comfort Heating, a heater that peaks in the lower wavelengths should be considered more appropriate in the first instance and will also consume less energy.
There are many other industrial uses for Near IR that make it entirely appropriate for this intensity of heat but this is out of the scope of this article.
Heaters that peak in the Medium IR wavelengths are suitable for intense drying applications (and other industrial uses outside the scope of this article) but are also less appropriate if the objective is to provide “Comfort Heating”. Again, a heater than peaks in the lower wavelengths should be considered more appropriate in the first instance and will also consume less energy.
Heaters that peak in the Far IR region (from 3 microns and lower) will be more appropriate comfort heaters and will consume less energy. Increasing the area under heat or the impression of its intensity can be achieved by adding the number of emitters in use, rather than using a more intense sort of lamp. Adding far infrared emitters will increase an area of comfort without actually increasing its overall temperature. It is wrong to think adding a higher intensity heater will increase the heated area and levels comfort: it will just increase temperature, locally.
Sources:
Soyun Cho, Mi Hee Shin, Yeon Kyung Kim, Jo-Eun Seo, Young Mee Lee, Chi-Hyun Park and Jin Ho Chung, Effects of Infrared Radiation and Heat on Human Skin Aging in vivo, Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 15 – 19;
Dr. Janet Voke, Radiation effects on the eye, Part 1 – Infrared radiation effects on ocular tissue, Optometry Today, May 1999
Intenational Commission for Non-Ionising Radiation Protection (ICNIRP). Health Physics Journal 91(6):630-645; 2006.