Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Spraying Lysol Into Ducts

I know Tom and Ray have advised spraying Lysol into ducts to kill

mold, mildew, etc.

I’ve got a 94 Sable Wagon. I sort of remember the CarTalk guys

saying that you spray the Lysol down into the area right under

the windshield where the wiper assembly (sometimes call a

transmission) is located. I assume removing that slotted cover

or cowl piece is a good idea. I’ve replaced wiper motors, so

I’m familiar with the procedure.

If (and that’s a really big “if”) I’m correct so far, it would seem

logical to turn the dash control to “vent” which brings outside

air directly into the passenger cabin.

One thing I am concerned about is whether the blower should

be on or off. The propellent in Lysol is flammable, which makes

the blower motor a possible ignition source. However, if the

blower is off I don’t see how the Lysol can be pulled into the


If I’m way off about this procedure, I would appreciate some


There is no need to remove the grate. Just spray into the area on the passenger side with the system set to heat or vent (just not recirculate or max A/C) and the fan on high to suck the lysol into the system.

I would recommend making sure the drain for that area is not clogged before you use the spray.  You need to start by making sure what blocked the drain in the first place is addressed before fixing the damage it caused.  If the drain is clear and you don't have leaves etc there to block the drain then you only need to turn on the blower to high and spray away.  

 Try lighting the lysol spray.  I doubt if you can ignite it.  Does it have a warning on the label?

No need to remove the cowling. Fan speed on ‘High’ when you do this. Don’t worry about the blower motor lighting up the propellant. The contacts in the motor are furthest away from the fan blades (squirrel cage), and air is pulled through the motor from a different source than the cowling. Propellant should never see any sparks.

Introducing these agents into ducting with the blower running is a manufacture supported technique. GM has provided a rather lenghtly description on how to do it with their cars and no mention of a fire hazard is given, and you know how these guys are with warnings. The one I can think of right now is the “do not eat” warning on silica gel packets.

Lysol itself is flammable I think, not just the propellant. One of the main ingredients is a high percentage of ethyl alcohol. When properly vaporized, perhaps by a hot heater core, it may even be explosive. So I would do this procedure carefully and not saturate the system with Lysol.

I’ve done it.

I suggest that you don’t spray a lot at once - just a quick spray once a month.

The first time I did it my car had the strong odor of Lysol for about a week afterward. It was worse than the odor it was supposed to eliminate.

What? you don’t like to smell like a rolling adult book store? GM has a real nice smelling product for this. The product is a bit expensive but there is a plus, instructions on the can. Available at your GM parts store.

There are better smelling and safer sprays on the market. Just go to your nearest automotive store and you will find quite a few, all with proper directions.

You need to have all windows or doors open, the A/C on full and the engine and fan running. Just spray the stuff in the grate for a pre-determined length of time. Shut the engine off, wait 20 minutes or so, and then repeat without spraying anything in, to purge the system. Repeat for the heater with the heater full on fan full on, etc.

A can of this costs a whole $12 and it good for at least 3 treatments.

Thanks guys!

I’ve got a can of Lysol and a bottle of Febreze in front of me. This wagon belongs to
my dad. He sprayed some Febreze directly into the dash vents. It masked the odor for
a few days.

I haven’t looked, but I’m not surprised auto stores carry these products. Smelly
ducts are a common problem, unfortunately. This 94 wagon may be old, but my dad
keeps it in great shape. He’s a wagon junkie! Several years ago he owned four.
He gave one to my nephew and sold another, so now he’s a two wagon man. How

The Lysol can does say its flammable and to keep it away from heat, sparks, and
open flame. I purchased the “crisp linen” scent which for some reason is a
tolerable odor, even inside the confines of an auto cabin.

From what you guys are saying, it seems safe to use as long as you don’t spray
too much at once. I’m glad removing the cowling is not necessary. That thing is
fragile. Hairline cracks are commom, as I’m sure most of you know.

I’ll try the Lysol. If the funny odors stay away for awhile the problem is solved.
If not, I’ll buy whatever they’re selling in the auto stores.

Something I’ve noticed about this problem which also applies to homes that have
forced hot air heating. The smell is always much worse when warm air is blowing
through the ducts. Frequently, people don’t complain about bad odors when they’re
using their AC in the summer. Not a surprise really. Bacteria and fungi thrive
when it’s hot and become dormant or die when exposed to cold air.

“Frequently, people don’t complain about bad odors when they are using their AC in the summer” FALSE. The Forum is swamped by posts from people with AC odor in the summer.

“Bacteria and fungi thrive when it’s hot and become dormant or die when exposed to cold air.”

Actually, at least in cars, it’s kind of like that, but with a twist: In the summer when the A/C is used, the moist environment from the condensate is perfect for growing bacteria and molds. That’s why A/C often has that musty smell. When you shut off your A/C, the temperature quickly rises in the evaporator pan and ducts to around body temperature or a little above, but moisture remains. The system can be a big petri dish.

In the winter, using the heat all the time dries it out and kills bacteria and mold. The hot, dry conditions are no place for microbes to live, and when you shut it off, the temp in the system plunges to whatever the outdoor temp is, further inhibiting growth. Warm air might bring out the smell, but the real nasties flourish during air conditioning season.