The real issue is with the hazardous substance urea-formaldehyde, which is used in the manufacture of MDF.
HPVA and CertificationIt is such a concern that MDF is often issued with what is called a HPVA Formaldehyde Emission Property Verification Certificate that essentially says that, yes, there is formaldehyde in the product, but it does fall below maximum formaldehyde emission levels. HPVA is the acronym for the Hardwood Plywood and Veneer Association, and its Reston VA-based lab conducts various types of tests (not just formaldehyde-related) on plywood, MDF, and other wood products.
It should be noted that the HPVA's formaldehyde test does not involve burning of MDF.
What Do Forum Members Say?Anecdotal evidence on remodeling forums reveals that there are two types of people who burn MDF: those who burn MDF simply to dispose of it and those who burn it because they want to heat their homes, chiefly with wood burning stoves. One forum member claims that he has burned MDF for "over thirty years" with no adverse health effects.
HPVA Lab's Opinion on the MatterI suppose that I am very much like Stephen Colbert in that I trust my gut, and my gut tells me that burning MDF is not a great idea.
With little hard information to base this opinion on, I contacted Brian Sause, Director of Testing, Certification, & Standards at the HPVA Lab, who said:
The makeup of a fiberboard panel is dependent on the desired properties of the final product. There is a high degree of variability in the products with regard to wood fiber content and alignment, adhesive or resin type used, and other additives to adjust the performance of the panels. I would agree that, as a general precaution, you should consider any composite material unsafe to burn in a household environment due to the unknown makeup. While there are concerns over high emitting products containing formaldehyde in an indoor air environment, toxicity of any combustible materials when ignited is a much greater concern.
HPVA's certification of engineered wood products ensures that they do not contribute to elevated levels of formaldehyde in the home. Formaldehyde naturally occurs in raw wood and even in the human body. A certification does not mean that the products do contain additional formaldehyde, but maintains that they are safe and controlled under anticipated conditions of normal use. For those who are concerned, there are many products available to consumers on the market today that are certified as No-Added Formaldehyde (NAF) and Ultra-Low Emitting Formaldehyde (ULEF) products.