I use them. I've heard the rumours about them being the cause of fires, but apparently, these rumours are false. See this link for more info.
SC Johnson released the following statement:
I have read postings on the Internet alleging that Glade® PlugIns® products have been involved in fires. Is this true?
SC Johnson recently learned that there have been postings on the Internet that have claimed that our products were involved in fires. It is important that you know that all of our PlugIns® products are safe and will not cause fires. We know this because PlugIns® products have been sold for more than 15 years and hundreds of millions of the products are being used safely.
Because we are committed to selling safe products, SC Johnson thoroughly investigated these rumors. First, we confirmed that no one had contacted SC Johnson to tell us about these fires or to ask us to investigate them. Additionally, we had a leading fire investigation expert call the fire department representative who is identified in one of the Internet postings. That fireman indicated that he has no evidence that our products had caused any fire.
We suspect this rumor may be associated with a past SC Johnson voluntary recall of one of its air freshener products, a Glade® Extra Outlet Scented Oil product that was sold for a short period before June 1, 2002. After discovering an assembly error in a small number of that product, SC Johnson implemented a voluntary recall and provided extensive information about the product to the U.S. Consumer Product Safety Commission (CPSC). After revising the manufacturing process and thorough testing for proper assembly, the Glade® PlugIns® Scented Oil Extra Outlet product returned to store shelves on June 3, 2002. SC Johnson has no knowledge of any credible reports of fire related to this product.
We also know that our products do not cause fires because all of our PlugIns® products have been thoroughly tested by Underwriters Laboratories and other independent laboratories and our products meet or exceed safety requirements. SC Johnson continues to work closely with the Consumer Product Safety Commission to investigate allegations involving PlugIns® products.
As a more than 100-year-old, family-owned company, SC Johnson is committed to providing top quality products that can be used safely in homes and we want to reassure you that PlugIns® products can be used with complete confidence.