Monthly Archives: March 2023

What’s in a chemical filter?

What’s in a chemical filter?

Current events certainly stimulate a lot of research, and the accidental release of toxic chemicals from storage and transportation units is no exception.  When a dangerous chemical is odorless and colorless, how can we possibly protect ourselves and the air in our homes?  Enter chemical filters, which are actually already available for purchase.

Many gas filtration media start with a base material and then add (impregnate) the base material with specialized materials.  Since all of these base materials have a multitude of miniature holes that can get “plugged up” with dust, it’s best to make sure the dust filter is clean and in place to preserve the life of the chemical filter.  The base material is incredibly light because of the vast amount of internal surface area it has in its many cavities and holes.  The way these materials  purify air is called “adsorption” (in contrast to absorption).  Adsorption and absorption both “suck up” liquids or contaminants, but there is a difference:  a sponge will absorb water, but eventually the water leaks out or evaporates.  Activated carbon, activated alumina and zeolites adsorb certain chemicals, some including water, but the adsorbed liquid or gas does not escape because a chemical bond is made, until the material is regenerated with high heat.  Since adsorption is a surface phenomenon, good adsorbents are those having large surface areas per unit mass and high attractive forces for the compounds to be adsorbed, called the solute. Although all molecules are adsorbed to a certain extent, those having high polarity are likely to be more strongly adsorbed than those having low polarity. Since water is a highly polar material, it is much more strongly adsorbed than hydrocarbons, for instance. (Air and Gas Drying with Activated Alumina)

Here are the most common base materials:

A main ingredient in these filters is activated carbon.  We’ve written about it here but when you have something more dangerous than sweaty socks or cat litter smells, we like to dig a bit deeper on its capabilities and limitations.  Activated carbon removes volatile organic compounds (VOCs) and acid gasses, which make them useful against a wide variety of pollutants.  To review, VOCs are compounds that have a high vapor pressure and low water solubility.  They are natural and human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. (  An acid gas is any gaseous compound which, when dissolved in water, will form an acidic solution.  Many industrial compounds are acid gasses, but did you know that we actually exhale an acid gas?  Carbon dioxide (CO2) is an acid gas, and activated carbon is a method for removing excess CO2 in a space.  

Base Material

Activated Carbon: around $1150 per ton (coconut shell)

What it adsorbs

VOCs, acid gasses



Lightweight and large surface area

Adsorption is lowered in humid environments

Fairly inexpensive

Filters exposed to the air eventually “fill up” with CO2 and water

Filters available in many sizes and price points

Not many consumer-grade activated carbon filters are “recycled”; regeneration of the media may or may not be possible depending on the chemicals adsorbed

Activated alumina is another base.  It’s a porous, solid form of aluminum oxide, otherwise known as Al2O3 or alumina. This is the same mineral that makes up the precious gems ruby and sapphire, with impurities being the source of the stones’ bright colors. After activated alumina has been evacuated of existing moisture by heating it, the high surface area and many pores of the material allow for the uptake of water and other molecules through adsorption.  (What is Activated Alumina?) At about 1.5 to 3 times the cost of activated carbon, activated alumina is pricier but very attractive for adsorbing different chemicals.

Base Material

Activated Alumina: around $1800-3600 per ton

What it adsorbs

Water, acidic gasses including CO2, and others



Lightweight and large surface area

Smaller range of adsorbed chemicals

High crush strength

Since it has a high affinity for water, moisture can reduce the capacity for adsorbing chemicals

Can also act as a catalyst for some chemical processes

Not many consumer air purifiers use this material 

Zeolites are another base material for chemical adsorbents.  They can be naturally occurring or man-made.  Zeolite has an aluminosilicate framework. Which simply means minerals composed of aluminum, silicon, and oxygen, plus countercations. This framework provides exceptional strength and stability to the honeycomb structure. It also makes it very difficult for the positively charged atoms (cations) to leach from Zeolite. (What is Zeolite?)   Molecular sieves are a type of zeolite that are manufactured to precise frameworks and pore sizes for specific applications.

Base Material

Zeolite: $1600-2200 per ton

What it adsorbs

Water, manufactured zeolite may adsorb VOCs if alumina is removed, molecular sieves can be even more chemical-specific



Lightweight and large surface area

Manufactured zeolites can be expensive

Less sensitive to water than activated carbon

Not many consumer air purifiers use this material but Austin Air is one

Higher crush strength than activated carbon

Well suited to low concentrations of VOCs

Molecular sieves can be tailored to the molecules they adsorb

Now that you know some of the base materials, additives (also called “doping”) can enhance capture/filtration of specific contaminants.  

  • Potassium Permanganate is added when sulfurous compounds may be present (such as hydrogen sulfide and sulfur dioxide).   According to this filter company, their molecular sieve impregnated with potassium permanganate oxidizes gaseous pollutants such as hydrogen sulfide, sulfur dioxide, formaldehyde, ethylene, mercaptans, and various aldehydes and alcohols.   Do you know what mercaptans are?  They are the sulfurous, rotten-egg smelling additives that are added to natural gas to help you know that there is a leak.

  • Potassium Iodide:  some AustinAir filters are impregnated with potassium iodide, for increased removal of formaldehyde and ammonia.  They are best used in places like new homes, laboratories, beauty salons, funeral homes, etc. Sources of formaldehyde in homes can be carpets, wood panel, construction materials and furniture upholstery, if not an outright chemical leak. (

  • Magnesium Dioxide and Copper Oxide: The air filter company Blueair adds these compounds in their activated carbon filters to remove carbon monoxide, ethylene oxide, and ozone.

So which filter is best for me?  It’s hard to plan for every scenario, but you may take into consideration the following:

  • This article/table by the California Air Resource Board (CARB) in response to the Aliso Canyon gas leak (California, 2015) describes what types of filters are in a number of high-end air purifiers.  The models may have changed slightly but it can give you an idea of how air purifiers can be used to reduce specific chemicals (mercaptans were judged to be the source of most peoples’ health issues).

  • If you live very close to a refinery or manufacturer of specific chemical products, you may want to find out what chemicals they manufacture, store and load, what VOCs/fumes are produced and what air filter is best to remove those VOCs. 

  • If you are interested in a particular type of filter, look for (or ask for) test data that verifies it removes what it’s designed to remove.  In an MIT study of 4 consumer-grade air cleaners, only 2 of them removed the VOCs toluene and limonene effectively.  

  • In the case of radon, activated carbon filters (and the others mentioned above) will not adsorb radon gas, but they will adsorb most of the radon decay products (termed “radon daughters or progeny”), which are actually the source of health issues associated with radon. (Reduction of Radon Working Level by a Room Air Cleaner).   Therefore, activated carbon is not recommended for first-line defense against radon infiltration into your home; a venting system is more appropriate and you should contact a professional if you have radon in your home.

  • In the end, activated carbon is widely used for a reason: it removes a lot of VOCs!  If you don’t have a specific chemical that you’re concerned about, this type of filter is a readily available, broad spectrum weapon against many pollutants.  If your air is particularly dusty, you’ll want to make sure that it also has a HEPA pre-filter to protect the activated carbon from getting clogged with dust.

Photo by Paul Teysen on Unsplash

“Sink” those microbes

“Sink” those microbes

According to a University of Reading study, sinks have the perfect recipe for a fungal environment and they host very similar organisms.  Researchers tested more than 250 restroom sinks for fungi, such as black molds and relatives of baker's yeast.  These fungal biomes usually don’t pose a problem for healthy individuals, but for those with compromised immune systems, sinks could be an overlooked reservoir of illness.  

One might think that with all the detergent and handsoap going down the drain, it would be squeaky clean, but for anyone who’s had to clean the drain or take it apart to unclog it or save a piece of jewelry, it’s anything but!  The types of fungi that live in sinks can tolerate high temperatures, low pH (acidic), and low nutrients. Some even use detergents, found in soap, as a source of carbon-rich food.  It’s a place with constant moisture and food sources, so…voila!  Mold galore.

If you’re concerned about the condition of your sink drain for yourself or anyone else living in your home, there are some simple ways to keep the drain clean on a regular basis without using toxic chemicals.  To be clear, the study was conducted on restroom sinks, but the principles are the same for every sink: eliminate food for mold and flush it with natural cleansers periodically.

  • Using a mesh drain strainer on your sinks prevents solids like hair from clogging it, because hair in  sink drains is just another surface for mold to grow on.   Sink Shroom is a sink stopper/filter that you can pull out, wipe it clean and replace to keep the hair out; tub and shower models are also available.

  • Plumbers agree: Never pour grease down the drain!  From cooking oil in the kitchen to any kind of body or hair moisturizing oil in the bathroom, it just doesn’t belong in the drain. 

  • Thoroughly rinse the drain with hot water when you send anything other than water down it.  Toothpaste?  Add hot water.  Extra dirty hands?  Add hot water.  You get the idea!

  • Natural cleansers can work great.  Better Homes and Gardens have compiled a list of natural cleansers and tools for every type of sink: stainless steel, porcelain sinks and white sinks are all covered. 

As with all other areas in the home, regular cleaning and maintenance of sink drains can go a long way!  If you still find mold growing around the drain or foul odors coming from it, then it could be a hardware problem instead.  All sink, tub and shower drains are required to be plumbed with a “vent”.  Vents allow sewer gasses to rise and escape through the roof of the home.  According to the uniform plumbing code, vents must be located within six feet of the P-trap (that snake-like part under the sink); otherwise, the drain may not work properly and gasses can build up, supporting mold and microbe growth.  If this seems to be the case, it’s best to have a good plumber check out the location and condition of the sink vents and see if there are other drain problems.  

Photo by Bibi Pace on Unsplash

All about Alkaline Water

All about Alkaline Water

Although I thought that alkaline water became a fad in the early 2010’s when it became readily available in the bottled water market, in fact it was almost 80 years earlier that scientists began to research the effects of alkaline and “ionized” water on the body.  To begin, let’s talk about what alkaline water is.

Water is super-important to our bodies and health, of course.  There are many properties of water, and pH ("potential of hydrogen" or "power of hydrogen") is one of them.  pH describes the acidity or basicity by measuring concentrations of the hydrogen ion, H+.  Chemically, water is made up of hydrogen and oxygen atoms sticking together in its famous “H2O” formula.  More free hydrogen ions in water (which are the proton of the hydrogen atom when it is stripped of its electron, denoted H+), cause water to be more acidic.  Water that has more free hydroxyl ions (OH-, read more about hydroxyl ions in the air here)  is basic.  Electronic pH meters measure the potential (electric charge) between 2 electrodes immersed in water or other liquids, to assess the hydrogen ion activity in the solution. (

The pH scale ranges from 0 (very acidic) to 14 (very basic) and the number 7–in the middle of the scale–is neutral, meaning it is neither acidic nor basic.  This seems simple, but this is not a linear scale–it’s logarithmic.  Each number represents a 10-fold change in the acidity/basicity of the water. Water with a pH of five is ten times more acidic than water having a pH of six.  The EPA recommends a pH of 7 to 8.5 for drinking water, and for reference black coffee has a pH of about 5 and typically handsoap falls between 8 and 10 (the soap shown below is likely soap used in automatic dishwashers).  Our blood is about 7.35 pH.   


Now that we understand a little more about pH, I can add a layer of complexity: alkalinity and pH are not the same.

The above chart shows relative pH, the concentration of acid protons [H+]. On the other hand, the alkalinity of a solution is its ability to neutralize acids. Alkalinity consists of ions that incorporate acid protons into their molecules so that they are not available as a free acid that can lower the pH. This is known as buffering.  (What is the relationship between pH and alkalinity?)  “Natural” or “mineral” waters contain higher concentrations of carbonate (CO32-) and bicarbonate (HCO3–) ions, which are the buffers, than purified waters. Thus they have greater alkalinity or potential to neutralize acids. 

Alkaline water is a very controversial topic because for some years, proponents stated that it changes the pH of your blood (to create an environment inhospitable to cancer and other diseases).  This theory is not true.  Our bodies tightly regulate the pH of our blood, and if it changed significantly, it would be a life-threatening condition, such as diabetic ketoacidosis.  Acidosis refers to having blood that’s too acidic, or a blood pH of less than 7.35, while alkalosis refers to having blood that’s too basic, or a blood pH of higher than 7.45. (  Alkaline water does not change the pH of the blood, however, only the urine.  This is because the acids in the stomach counteract the alkalinity in the water, before it is absorbed by the body. (

Although research is ongoing, the more plausible cause of health benefits from drinking alkaline water is its acid-neutralizing and antioxidant potential.  There are several ways to make tap water more alkaline: electrolysis, light irradiation, ultra-sonication, treatment with a magnetic field, bubbling with gasses, collision, strong water flow, and treatment with specific minerals or rocks (2012 article).  Of these, electrolysis (ionization) and mineral treatments are probably the most popular.

Regarding mineral treatments, increasing water alkalinity can be as simple as adding a small amount of  baking soda, but this method is not particularly tasty to everyone and adds sodium as well, which can be detrimental for those on low-sodium diets.  Chemical water treatment systems add alkaline minerals such as calcium, magnesium and potassium through concentrated drops, powder supplements or water filters.   Ionization, however, is where scientists and commercial businesses have been busy testing and innovating for the better part of the last century. 

Alkaline water research began in Japan in the 1930’s.   Japan has been a major adopter of alkaline water for health benefits, where alkaline electrolyzed water (AEW) apparatus have been approved as a medical device.  The Japanese Health Ministry recognizes that alkaline electrolyzed water (AEW) improves gastrointestinal health. It neutralizes gastric acid, improves intestinal bacterial flora and improves other gastrointestinal conditions.  (Japanese Study of Daily Ingestion of Alkaline Electrolyzed Water). 

According to an ionizer manufacturer, water ionizers work by using electromagnetism to change ordinary tap water into ionized water.  Ionizers actually need calcium and magnesium in water to work. They work best with hard water as long as the water isn’t too hard. If it is, then the hardness will need to be reduced. Water ionizers are actually more prone to hard water deposits because an ionizer changes the mineral carbonates in tap water into mineral hydroxides. (Will a water ionizer work with my water?).  Plain water, besides the H2O,  is a mix of alkaline minerals and carbonate (dissolved CO2). A water ionizer separates the carbonate from the alkaline minerals. The alkaline minerals and the acidic carbonate are discharged in  separate streams of water. (How water ionizers work)  

To put it another way, a water ionizer puts a negative electrical charge into the water it makes. As a result, that negative electrical charge gives the water antioxidant potential which can be measured, just like the charge of a battery. The negative charge is called its Oxidation Reduction Potential (ORP). (What is the difference between alkaline water and ionized water?)  

Now that you theoretically know how to make alkaline water, you might want to investigate some of the latest studies on benefits of drinking it:

A 2020 clinical trial found that alkaline water consumption (pH of 9) for 10 months in mice had an anti-aging effect by increasing telomere length (which regulates cellular aging) and significantly reducing reactive oxygen species in blood. (Alkaline Water Benefits: Three Surprising Research Findings)

A clinical trial published in the Biology of Sport journal found that athletes who consumed alkaline water had “favourable changes” to hydration status compared with athletes who drank tap water. The group drinking alkaline water also had much more efficient lactate utilization, which suggests that alkaline water use during exercise may potentially improve endurance. (Alkaline Water Benefits: Three Surprising Research Findings)

A 2021 study on high-mineral alkaline water found that its consumption improved anaerobic exercise performance, supporting the potential performance benefits shown in the previously-linked study. (Alkaline Water Benefits: Three Surprising Research Findings)

A 2022 study found that postmenopausal women who drank alkaline water had significantly lower metabolite risks (fasting plasma glucose, TG/HDL, diastolic blood pressure, waist circumference), longer sleep duration and stronger handgrip strength.  However, there was no significant difference on LDL, systolic blood pressure and body weight with alkaline water drinking.

Despite these and other studies, many scientists and health experts are not convinced that drinking alkaline water has benefits.  They don’t think it’s unsafe to drink, however, so you’re free to do your own experiments and research.  Let us know about your experience with consuming alkaline water!

Photo by Johnny Z on Unsplash