You see it on light bulbs and plenty of other items but what’s that UL stand for? It stands for Underwriters Laboratories based out of Northbrook, Illinois. UL certifies, validates, tests, inspects, audits, advises and educates and has done so since 1894.
You know it as the cure-all for all things immoveable or getting rid of pests. But do you know what the acronym means? The WD part means water displacement and 40 comes from the number of attempts it took to get the formula worked out back in 1953.
The shorthand has overtaken the longer version of heating, ventilation and air conditioning and for good reason, that’s a mouthful.
Check these things before calling an HVAC technician to avoid looking foolish and figure out just which kind of furnace filter is the best.