Most traditional car air fresheners consist of a small, scented piece of cardboard with a string through the top.  Car Freshner’s Little Trees popularized this method of disposable freshening when they invented the iconic evergreen cardboard cutout in 1952.  Traditional cardboard car air fresheners release their fragrance when exposed to the air.   When completely removed from their plastic bag packaging, the fragrance can be overpowering, and the life expectancy short, with the scent lasting several days to a week.   Cardboard air fresheners are also limited by where they can be safely used.  Cardboard air fresheners are made to be hung-up, contact with other surfaces could cause damage to the surface with which they come in contact.

One additional consideration

If you want a quick shot of air freshening, a traditional cardboard freshener will do the trick.   However, the cost advantage of this air freshener type quickly disappears when you may have to buy multiple cardboard air fresheners to equal the freshening power of a longer lived vent stick, can (gel) style or fragrance oil based air freshener.

A newer variant in paper is a wafer thin scented paper car air freshener.   These air fresheners use a specially woven paper blend that both absorbs and permeates fragrance oil.   Typically used in under seat applications, wafer type air fresheners are discrete and deliver a strong initial scent.  Owing to their paper composition, they are also extremely cost effective.  However, like hanging cardboard air fresheners, the scent fades quickly when exposed to the air and heat in vehicle’s interior.

For most applications, you might want to consider a longer lasting can (gel) or oil based wick or diffuser.

Automotive spray fragrances are handy for clearing the air from time to time. Aerosols don’t last as long as some other options but they are fast. Like their home counterparts, spray fragrances are a quick way to temporarily freshen your car’s air.  Aerosols come in various types including, fragrance only, fragrance with odor elimination and air sanitizing.    Fragrance only aerosol sprays mask odors with a pleasant smell.  Fragrance and odor eliminating products like FebrezeÒ encapsulate malodor particles, leaving behind a fresh scent. 

Another class of aerosol is the air sanitizers.  These products may include a fragrance, however, the primary claim they make is that they freshen the air by killing odor causing bacteria.   Any claim of  killing bacteria requires EPA registration.

In general, aerosols offer complete coverage.  You spray it up into the air and it slowly envelops the whole space, right down to the floor.  Aerosol car air fresheners can also be sprayed directly onto a surface such as a car seat for targeted freshening.   
But like many quick fixes, the effect is temporary, usually requiring a re-spray to maintain the fragrance experience.  Repeated use of an aerosol spray will result in build-up on interior surfaces requiring more frequent dusting and cleaning.

If you need a quick burst of freshening to mask a bad odor, aerosol air fresheners work well.  If you are looking for a longer lasting fragrance experience that does not require repeated applications, consider another car air freshener type.

Sticky Gel air fresheners are made from a sticky, solid plastic gel-type that encapsulates the fragrance oil.   Sticky gel type air fresheners like “The Bug” from HandStands literally sticks to almost any surface in your car without adhesives.  They are removable, reusable and are handy for placing in hard-to-reach areas, such as under the dash.  Since Sticky gels do not use the air vents of your vehicle and therefore are not as effective in delivering as satisfying a fragrance experience as vent mounted options, but do have a longer life that cardboard, paper or aerosols.  As the newer scented oil wicks and diffusers technologies have become more widely accepted in the market, the popularity of sticky gel air fresheners has diminished.   Further limiting their market appeal, is the limited number of scents.

Electric car ionizers are typically more expensive than the other car air freshener options.  Ionizers plug into your vehicle’s 12 volt power outlet and come in two basic types, those that filter and those that produce ozone.   Filtering type ionizers generate a static charge on a collect plate that attracts the negative ions in dust, pollen and bacteria.  The static charge is relatively weak so only particles very close to the ionizer are attracted and collected.   Ozone type ionizers produce O3, which readily bonds with dust, pollen, etc. to improve the air quality and eliminate odors.

Although popular, the effectiveness of these types of air fresheners is open to debate.  Regular dusting and vacuuming of your vehicle’s interior combined with the use of a vent stick or oil based wick or diffuser air freshener type can be a cost effective alternative to electric car ionizers.

Vent stick car air fresheners as the name implies are design to fit into your vehicle’s air vents.   Soft, scent infused plastic is combined with an alligator clip type frame to slide into car’s air vents.  Air from your vents passes over the soft plastic releasing the fragrance.  Due to their small size and low cost, fragrances can be easily combined to increase the amount of freshening and create a unique sent.    Because the fragrance oil is encapsulated in soft plastic, vent sticks are easier on your vehicle’s interior surfaces than hanging cardboard or paper.

Vent sticks provide a good fragrance experience, but cannot match the superior fragrance performance of oil based wicks or diffusers.  That said vent sticks are a discrete, cost effective alternative to hanging cardboard, paper and aerosol air fresheners for cars.

Can style or scented gel air fresheners are relatively small in size and have a plastic or metal lid with air holes.  Under the lid is a protective cover, which is removed before use.   Some brands like Refresh your car! brand scented gels include an adjustable plastic lid so that you can control the level of freshening and extend the life of the air freshener.   Typically inside the can is a gel like base although some brands use a fiber material.  This gel or fiber is the air freshener.   Scented gels are one of the most versatile types of car air fresheners.  They can be placed under seats, in consoles, or in the trunk of car.   Scented gels provide a good fragrance experience and have a long life than other air freshener types.  For maximum effectiveness, scented gels should be placed in areas with good airflow and checked once a month.

Scented gels are ideal for RV, home, office, gym or locker use.    For more fun and interesting ways to use scented gel air fresheners, see the fun with fresheners tab.

Oil wick or scented oil wick car air fresheners are one of the more recent developments in disposable freshening.  Fragrance oil is placed inside a glass bottle.   A porous wick is inserted into the oil which transports the oil through a collar into a plastic top, which clips into your car’s air vents.   The plastic top contains small louvers, which can be opened and closed to control the amount of fragrance released.  In a dual or tri scented product, the scent control regulates how much of each scent escapes into the air.

Although scent oils may cost slightly more than other air freshener types, the quality of fragrance and their longer life expectancy make them a cost effective alternative to fresheners with a shorter life.  Oil wick car air fresheners are ideal for any size car, truck, SUV or RV.

The latest advance in automotive air freshening technology is the Diffuser.   Diffusers use fragrance oils in a plastic container that is backed or sealed by a semi-permeable membrane.   Diffusers attach or clip onto your vehicle’s air vents using the circulating air to “push” fragrance into the cabin.   Diffusers come in a variety of sizes and shapes plus single and multi-scent versions.   Often Diffusers offer scent control allowing the user to control the exact amount of freshening or the amount of each fragrance to emit.   Diffusers with scent control offer the most flexible in scent customization of all the air freshener types providing a stable and long–lasting fragrance experience.   Diffusers longer life equals a lower total cost of ownership.

Auto plug-in air fresheners use the power from your car’s power outlets to warm a soft plastic containing fragrance oil to release their scent and freshen your car’s interior.   Some models have built in lights and while others have adjustments.

Since these fresheners require a car’s power outlet, they are not as flexible as to where they can be placed in your vehicle as other car air freshener types limiting their effectiveness.