Do Rodents Affect Indoor Air Quality

Animal dander, bacteria, mildew, molds, viruses, pollen, mites, cockroaches, and house dust are biological contaminants. These pollutants come from various sources. Animal dander and saliva come from household pets, animals, people, plant and soil debris are sources of bacteria, plants produce pollen, while animals and people transmit viruses. So, do rodents affect indoor air quality?

Do Rodents Affect Indoor Air Quality
Do Rodents Affect Indoor Air Quality

One of the most potent biological pollutants is the protein in urine from mice and rats. The protein can become airborne once it dries up. Mildew and mold can breed in a contaminated central air system and be distributed throughout the home by other sources of biological contaminants.

The growth of some of these contaminants can be minimized by regulating a home's relative humidity (RH) level. The recommended relative humidity level for most homes is 30-50. Molds, bacteria, and insects find the perfect breeding ground in wet surfaces, water-damaged materials, and standing water.

Warm, damp environments are an ideal breeding ground for house dust mites which are the sources of some of the most potent biological allergens.

Biological Pollution
Biological Pollution

The Health Effects of Biological Contaminants

Allergic reactions such as allergic rhinitis, different asthma types, and hypersensitivity pneumonitis result from biological contamination. Chickenpox, influenza, and measles are infectious illnesses transmitted through the air. Some common biological pollution symptoms include digestive issues, lethargy, shortness of breath, sneezing, and dizziness.

Allergic reactions may become apparent after the repeated exposure to a particular biological pollutant. However, multiple exposure or re-exposure over time may lead to an immediate reaction. Consequently, people who have only experienced mild to no reactions may become sensitive to particular allergens.

Exposure to toxins from microorganisms that typically grow in ventilation systems in large buildings can lead to humidifier fever. Some microorganisms that thrive in humidifiers and home heating and cooling systems could also be responsible for such diseases. People that are more susceptible to these kinds of agents include older people and children.

Asthma can be triggered by pet dander, dust mites, mold, pest droppings, or body parts. A large number of the population suffer allergic reactions from biological contaminants such as pollens and molds.

Breeding Ground
Breeding Ground

How To Reduce Exposure To Biological Contaminants

It is essential to maintain the cleanliness of the home and heating and air conditioning equipment. Efficient air distribution and adequate ventilation are also vital. Moisture control is the key to mold control. Get rid of excess moisture and water, then get rid of the mold if it's causing issues.

To control cockroaches, mold, and dust mites, maintain RH at 30-60%. To control animal and insect allergens, seek the services of professional pest management.

Here are some ways to reduce exposure to biological contaminants.

– Ventilate crawl spaces and the attic to get rid of excess moisture. Water condensation on building materials can be prevented by keeping a humidity level of 50% in these areas.

– Bathrooms and kitchens should have exhaust fans vented to the outdoors. This ensures that most of the moisture present during day-to-day activities is dried up.

– Follow manufacturers' instructions when cleaning ultrasonic humidifiers or cooling mist. Make sure they are refilled with clean water every day. Humidifiers can cause diseases like humidifier fever and hypersensitivity pneumonitis since they can become ideal breeding grounds for biological contaminants.

– Remove, dry, or replace water-damaged carpets and other building materials. Bacteria and mold can find the perfect building ground in water-damaged building materials and carpets.


To avoid the risk of diseases caused by rodents, make sure you keep the house clean and take extra steps to reduce the risk of biological pollutants in your basement. Clean and disinfect your home and basement regularly.

How Often Should a Furnace be Serviced?

Winter is inevitable every year and the only way to get through it is by having your home’s gas furnace in proper condition before winter comes knocking on the door.

Nothing beats a chilly day more than turning on your heater that is working properly. You will feel yourself defrost almost immediately! This is just one reason why regular gas furnace maintenance should be a priority for many homeowners. For those who do not prioritize their furnace maintenance, they can run into issues or problems getting their furnace to run properly. Any issues or problems with a furnace can be quite pricey which would result in needing financing for HVAC replacement.

Talking about problems, around 75% of HVAC system issues arise from poor furnace maintenance. Homeowners fail to find out the answer to, ‘how often should a furnace be serviced?’ due to the fact that furnaces are seldom used. This is the main reason many furnaces tend to arise issues with usage. But, before you learn about how often you need to service your gas furnace, you will need to understand why it is so important to ensure it gets done. There are many risks involved when you do not get your gas furnace regularly serviced.

How Often Should a Furnace Be Serviced?
How Often Should a Furnace Be Serviced?

Risks of Not Servicing a Gas Furnace Regularly

Most of the problems that homes suffer are usually a result of a gas furnace that is in poor condition. With that being said, you can avoid this by getting regularly scheduled furnace maintenance. There are some risks involved with not having your furnace regularly schedule and those are:

Risk of Cracking the Heat Exchanger

You ought to know that this is the most dangerous risk posed by the negligence of the gas heat furnace for too long.  If the heat exchanger is cracked, poisonous gases like carbon dioxide, carbon monoxide, soot and even nitrogen oxides can be released into the air in your home and when in the right amount, these gases can cause irreversible harm to your family.  This problem can be caused by a host of factors including a clogged filter and more. That is why regular maintenance of the gas furnace is paramount.

Temporarily or Permanently Ruined Pilot Light

A faulty pilot light may be due to the gas valve not being properly opened because the light button isn’t properly pressed, or a clog caused by dirt in the pilot opening. A professional gas furnace technician should know how to inspect and clean all areas surrounding the pilot light as well as clear the valve-ways for better functioning.

Dusty or Dirty Filters

Just like debris can spoil the water heater filter, over time, dust and dirt will gather in your furnace air filters and the machine will have to be coerced into putting extra work to warm your home during the chilly periods. This extra work can cause the machine to break down or lose its efficiency as the case may be. Your HVAC professional should be able to offer free filter change for your gas furnace every 2-3 months as failure to do such can cause a bunch of problems.  

Benefits to Regular Gas Furnace Maintenance:

Power Bills Would be Reduced as Energy Efficiency Increases

Take Sacramento winter for instance. The amount of heat used would only result in huge power bills and this might upset your financial plans. However, with proper and regular maintenance, your gas furnace would work at peak efficiency and bring about a considerable reduction of your energy bills.

Forestalls Huge Expenses of System Repairs

Once you realize and pay attention to how often a furnace should be serviced, you can forestall any future expenses that might result in your HVAC system breakdown, especially in the future. Small issues like clogged filters when not properly fixed can lead to greater problems with time which will definitely incur more expenses. The only way to avoid this situation is to be proactive especially in the fall when such small fixes on a gas furnace aren’t expensive.

Extension Of Your HVAC And Gas Furnace Lifespan

If your gas furnace, as well as the HVAC system, is free of minor issues like cracks, clogged filters and others, it can help the machine to run efficiently for long. It can also save you money that you would have spent in a replacement of a part or total overhaul of the system.

So, How Often Should A Furnace Be Serviced?

The problem with some folks is that they think because the HVAC system is still running smoothly, all is well. They are just ignorant of how often a furnace should be serviced and before they realize it, there must have been problems that add up to cost too much for comfort.

So, if you’re asked how often should a furnace be serviced, what would be your response? Most professional would recommend it once a year. However, if it is possible, your gas furnace should be serviced both in the fall and spring.

Gas Furnace Maintenance
Gas Furnace Maintenance

How is a Gas Furnace Serviced?

It is important that you contact a licensed professional who knows how to service a furnace to handle yours. He/she would advise you on how often to service a furnace so you do not end up paying stupendous amounts to get your home gas furnace working properly again.

Besides reaching out to an expert, if you want to carry out DIY maintenance on your gas furnace, you need to make sure you understand the workings of a furnace. It can be quite dangerous to handle maintenance on your own.

If you are a HVAC professional, then having the right tools and apps for your HVAC Company will also allow you to work more efficiently.

Are Energy Efficient Windows Worth It?

When it comes to energy saving windows, there are some important factors to be considered before purchasing one, such as the energy efficient window costs.

High efficiency windows will presumably reduce your bills, but are energy efficient windows worth it? Continue reading to find it out.

Are Energy Efficient Windows Worth It
Are Energy Efficient Windows Worth It

High Efficiency Windows

Most energy efficient windows work thanks to the following elements:

  • Number of Panes

Energy saving windows will have even up to three panes to protect your home, while most old window designs will only have a single glass pane that lets the heat out during winter and doesn’t keep your home cool during summer, which is particularly necessary if the ozone layer is still declining.

  • Insulated Glass

High efficiency windows include an inert gas in between the glass panes that reduces the amount of air that is transferred into and out of your home due to its high density. Moreover, this type of glass can reduce heat loss during winter and heat gain during summer thanks to a thin layer of metallic oxides that control infrared light and reflects the ultraviolet rays, which are caused by the ozone depletion and may impact your health.

  • Frames

Due to their poor heat conduction quality, most efficient windows feature a fiberglass or vinyl frame, which will provide your home with better insulation. On the other hand, the aluminum frames in old windows allow air to easily pass through.

  • Installation

Are energy efficient windows worth it? Yes, however, it doesn’t matter that you get the best energy efficient windows if they’re not installed properly. Therefore, make sure to hire a highly-experienced installation team to be able to see energy savings.

Energy Efficient Window Costs
Energy Efficient Window Costs

Saving Money with High Efficiency Windows

It is estimated by the U.S. Department of Energy that replacing double-pane windows with energy saving windows in your house will help you save from $27 to $111 every year. On the other hand, replacing single-pane windows can help you save you from $126 up to $465 every year. Nevertheless, the location of your home also plays an important role. In colder states, you save around $150 while in warmer states you can save up to $250. As the average replacement cost is around $150 per window, it’s possible you might see savings after two years, as it also depends on how many windows you have at your home.

Energy Saving Windows: Benefits

According to research, are energy efficient windows worth it? Well, homeowners report that up to 75% of exterior noise and sun damage to your carpets and furniture are both reduced with high efficiency windows. Furthermore, these windows add value to homes and contribute to monthly savings.

Therefore, besides knowing when your thermostat is bad and needs to be replaced, the most efficient windows will help you to control your home’s temperature.

Best Energy Efficient Windows

What type of window is the most energy efficient? Thanks to the Energy Star rating, you’ll be able to compare window performance. All windows will either meet or exceed energy code requirements, which will help you to make a decision.

Furthermore, based on your geography and climate, you can look up the best windows for you after checking some more technical elements such as the fraction of solar radiation that passes through the window (solar heat gain coefficient) and the rate of the window’s non-solar heat loss or gain (U-factor). Make sure to ask a window company in your city to know which energy efficient windows are available.

Energy Saving Windows
Energy Saving Windows

Parts of an Air Conditioning System

From the dawn of man, our discovery of fire has opened our eyes to how much of our comfort can be regulated. We make buildings to keep us cool under hot weather, and the fire keeps us warm during the cold. Our advances in science and engineering have improved our understanding of the operating principles that keep the world running.

We have developed a variety of ways to keep our living spaces as comfortable as possible through the scientific method. Now we can control the temperature, airflow, and humidity of our homes and workplaces through centralized heating, ventilation, and air conditioning.

Before we got here, much of our comfort relied on the natural flow of hot and warm air around buildings, which was difficult to control. However, lately, we have peaked in the efficiency of air conditioning systems. Maybe we should explore how they work, especially if you need to maintain, repair, or replace parts of an air conditioning system.

The Refrigeration Cycle

Parts of an Air Conditioning System
Parts of an Air Conditioning System

Cooling the interiors of buildings requires a refrigeration cycle. Of all the parts of an air conditioner, this is one of the central A/C components. According to the air conditioning basics, it works by circulating refrigerant between the exterior and interior parts of an air conditioner unit. This also goes for getting fresh air in sunrooms especially if you decide to add another A/C unit.

Simply by using electricity as its power source, the refrigeration cycle relies on a pumping unit to circulate the coolant through pipes and refrigeration lines to the interior of the house. Internal temperature is regulated by directing the flow of conditioned air through ducts to each room and collecting the warm air to be released outside.

The process starts with warm air inside the house drawn by a motorized exhaust fan and fed to the ductwork. The coolant in the refrigerant lines is pumped from the exterior compressor coil; at this stage, it is cold and in a liquid state.

It is delivered to the interior evaporator coil, which is located near a heat source or directly flowing through the ducts absorbing heat from the warm air and cooling it down. The cooled air in the ducts is pushed through connecting ducts leading to individual rooms by motorized supply fans, and the house is cooled down evenly.

The coolant evaporates after absorbing the heat from the interior air and is pumped back to the compressor coil outside. The motorized exhaust fan then sucks the cooled air inside the house, and the cycle repeats continuously to keep the temperature cool as set by the thermostat. This is a good way of checking if your home thermostat is bad.

Parts Of A Central A/C System

To get a better picture of the mechanisms that run air conditioning, we should check out the different central air conditioning components. Typical parts of an air conditioning system are split in two, and these are the outdoor and indoor components.

Outdoor components contain the condenser, compressor, electrical components, and a coil. The compressor’s work is to cool the refrigerant below its vapor point so that it remains liquid. It is complemented by a series of condenser coils to expose the coolant to as much surface area as possible in a small space.

This slows down the flow of the fluid and cools it faster. Electrical components include the power supply and automatic control units that regulate the rate and volume of airflow, as well as the amount of coolant being circulated to achieve the desired cooling or heating effect that is needed.

The evaporator coil is usually installed on top of the gas furnace inside the house. It is pivotal to heating the interior air during cold seasons but also helps in regulating humidity. A series of pipes and ducts connect the interior to the exterior components, which circulate coolant and airflow between the important parts of an air conditioning system.

Air conditioning refrigerants hold the critical role of heat transfer, making them responsible for all the heating and cooling effects we want. Ducts and vents in the floors, walls, and ceiling act as air tunnels for ventilating the different rooms.

Finally, the automatic control unit powers the whole process. A thermostat on the user’s end is the primary input for the system. The temperature setting it is given affects the operation of fans, humidifiers, and pumps.

This is, in fact, where capacitors play a special role. You may be asking yourself, “what does a capacitor do in an air conditioner?” Well, they are responsible for providing a high voltage power source to give the motorized fans a high-speed start. Electrically driven pumps circulate the coolant between the evaporator and condenser coils through the compressor.


Central A/C Components
Central A/C Components

Thanks to this innovative order, air conditioning systems have benefited our lifestyles in a myriad of ways. For instance, central air conditioning keeps our homes warm during the cold, cool during intense heat, and as humid as comfortably possible during dry spells.

In addition to this, an advanced A/C system would have sophisticated filters that remove dust and other microscopic pollutants from the air flowing through our homes. Finally, with the compressor units being installed outside, the noise levels during operation are significantly reduced.

This provides quiet, pleasant operation. Air conditioning systems that use less power to produce a greater cooling effect should be preferred as they have a higher SEER rating. If you are needing to get a new HVAC system and can not afford the price upfront, you should look into financing for HVAC replacement before scheduling for a HVAC professional to come out.

How to Get Fresh Air in Sunrooms

A sunroom in your home allows you to enjoy indoor living with great outdoor views all year round. It is the ideal place to relax, read, entertain, or dine in. But to fully enjoy the structure you must know how to get fresh air in sunrooms. Read on for five ventilation ideas of how to get fresh air in sunrooms for joy and comfort this summer.

How to Get Fresh Air in Sunrooms
How to Get Fresh Air in Sunrooms

1. Sunroom Ceiling Fans

Ceiling fans are a versatile top-rated ventilator option for all types of sunrooms. The fans make the room breezy while adding character and style to the ambiance. Sunroom fans are now designed with additional functionalities to aid circulation. They add elegance and lighting to the room.

Sunroom ceiling fans are affordable and energy-friendly. They are suited to power different sizes of rooms. Ceiling fans can be used indoors or outdoors to circulate air at various speeds in all seasons. The blades of ceiling fans are set to function in reverse during cold weather to whip the warm air gathering up back towards the ground. Some ceiling fans provide lighting too.

In a solarium or conservatory, where there are no doors or windows to be opened, vent fans are more suitable. The vent fans work in a similar way to exhaust fans, expelling hot air that collects towards the roof outside. Vent fans can also be used in sunrooms and where there is a very steep roof.

2. Indoor Air Conditioning

Air conditioning within the house could be extended for use in the sunroom. When existing home air conditioning is not available for the sunroom, there are other room ventilation ideas. For example, acquiring a portable air conditioner with a cooling capacity matched to the room size.

3. How To Get Fresh Air In Sunrooms With Natural Circulation

Entrances to the sunroom from the main house may be closed and opened to regulate air circulation. Managing any available entrances is an energy saver. The doors or windows may be left fully or partially opened to allow the free flow of air. Screening and meshing of windows also allow air and light to stream into the room. Security systems for the sunroom and screened patio that allow the door to be partially open also offers effective ventilation.

4. Fans For Screened Porches

Screening a porch is an easy and common way to ventilate, enclose, and keep out the bugs. A fan with large blades will whip a breeze on the porch and blow away any insects. Enclosure size and lighting are a consideration when choosing the fan to install. The power of the fan is tailored for energy efficiency since it is more powerful in an enclosed area. It can also be fitted to provide additional light. Screened porch fans should be chosen for best fit and enhanced efficiency.

How to Get Fresh Air in Sunrooms
How to Get Fresh Air in Sunrooms

5. Patio Air Conditioners

Patio AC’s allow you to feel a constant cool airy breeze while enjoying your outdoors. Patio air conditioners are also known as outdoor air conditioners, evaporative coolers, or swamp coolers. Cooling occurs when a fine mist of cold-water droplets is spewed into the air with the temperature falling by as much as 25-30degrees. Evaporative coolers are low energy users and environmentally friendly. Patio air conditioners cool in hot weather and humidify in winter if they have proper refrigerant. Consider the size of the space you want to cool before selecting the best outdoor air conditioner.

Which One Will You Use?

Whether you have a screened in porch or a sunroom, you will find great use of these methods for how to get fresh air. Keep in mind when using an outdoor A/C system that the refrigerant used could cause ozone depletion and could have potential side effects on your body and health.

Those are our 5 best methods for how to get fresh air in sunrooms. Which one will you use?

What is a Water Heater Filter

To safeguard your appliances, you need to keep the minerals inside the solution preventing damage from your water heater. This is where a water filter is necessary to help retain these materials. In essence, it functions to retain the minerals dissolved in the water. In this article, we’ll uncover how to use the water heater filter and how to maintain them. 

What is a Water Heater Filter System? 

Many people get confused when they hear the word filter. A hot water heater filter tries to fend against scaling using safeguarding the filter at top of hot water heater. Scaling in the heater can destroy many types of water heaters. Filters for hot water heaters are anti-scale items that are incredibly effective. 

What is a Water Heater Filter

How Do They Work? 

A water heater filter system is a mechanism that works to keep the hardness from the minerals inside of a solution. This is necessary, so it doesn’t leave the solution and move up on the heating components or on the bottom portion of the heater. By using a hot water tank filter, you can use its scale inhibitor to safeguard against the scales building up inside of the orifices. 

What Are They Used For? 

Hot water filters for water heaters are used to keep the longevity of your water heater. Without this, hard water will come up inside the heater forcing minerals to come out. This develops a rock in the water heater. Your water heater becomes ineffective until it no longer functions. A water heater filter will retain those minerals in the solution and keep your water heater effective. 

What is the Installation Process? 

You need to install a filtering system in your water heater by placing it on the waterline. This line feeds the heater to remove minerals or block the minerals before any scaling may happen. These filters are boxed in on the filter housing. If you use scale net filters, it can be installed on the cold water line to have the water heater fed. 

What Can it Filter Out? 

It can be tricky, but filtering systems do not filter anything out. Instead, it keeps the minerals in the solution. However, the filter does block dirt and debris from getting inside of the heater. This is why you should install a filtering system to block it from coming in. These filters also help with the ozone and cleaner air

When Does it Need Replacement? 

You should replace your water heater filtering system once a year. This is because the phosphate mineral will dissolve and eventually pass through the filter. The minerals will dissolve and no longer effectively protect scaling. This means you need to replace the filters at least once a year continually. But some products like a TAC product or scale net can last you three to five years. But this is dependent on how much hardness is in the water and the amount of water that gets through. 

What is the Root Cause of Scale? 

Water hardness is the root cause of scaling. Since a water heater is extremely hot, minerals such as magnesium and calcium inside of the hard water want to get out. These minerals will want to get out and latch onto the heating element’s electricity. This will settle on the bottom and block the path of a heater. Be careful because water heaters will stop working properly due to having to fight off the scaling rather than try to heat your water supply. 

The best solution for this problem is to use a water softener. The water softener will safeguard your water heater to remove minerals. But if you just want to protect the heater, then just use filters and scale inhibitors. The filter is eco-friendly and helps to protect the ozone layers

How Does Sediment Accumulate in Your Water Heater? 

By putting a filter, you will be able to catch all of the sediment and debris. This is vital if you utilize a city water supply or well water. This can be a detriment to all of your fixtures like your toilets, showerheads, and dishwater. These heaters contain a drain on the bottom. One trick is to turn off the water and drain the debris out or clean it out. This debris could end up causing a huge flooding accident in the basement

How to Flush the Water Heater and How Frequently Should You Do it? 

You don’t need to flush your water heater very often, contrary to popular belief. The best way is to simply use an anti-scale product or water softener to safeguard against debris and unwanted sediment. If the debris builds up, you may turn the supply off and clean out the drain from the bottom. You can use a hose from the garden and have the water run to the sink or the garage. The frequency in which you are flushing depends on the amount of debris that has been built up. When draining, you can twist the inlet and stir the water, so the debris is drained out. 

What is a Water Heater Filter

R22 vs R410a Refrigerant

What is the difference between R22 vs. R410a refrigerant coolants? How they can affect the cooling and/or heating systems in your house?

How Was It That R22 Changed To R410a?

R22 was used in air conditioners for decades. Now companies are phasing out R22 for R410a. The trouble with R22 is that it is both less productive and less sustainable than R410a Freon. The step away from R22 refrigerant by the government is an attempt to make homes more productive and reduce greenhouse gas pollution, because R410A does not contribute to ozone depletion.

R22 Vs. R410a Efficiency

For R22, governments aim to replace all the old R22 refrigerant for the R410a. Nevertheless, aside from regulation, which of the two cooling solutions is a safer choice for homeowners?

R22 Refrigerant

  • Since 2010, because of the R22 refrigerant phase out, the R22 is no longer used by air conditioners and heat pump manufacturers.
  • R22 can no longer be manufactured or produced since 2020.
  • R22, which is less capable than R410a coolant to absorb and release moisture, leads to the degradation of the ozone, thereby making it less energy efficient. The price of R22 continues to increase, with the remaining supply declining.

R410a Refrigerant

  • R410a arrives with both newly designed heat pumps and air conditioners.
  • In comparison to R22, R410a does not lead to ozone depletion.
  • R410a consumes and removes heat faster than R22, which makes it energy-efficient to use.

Because R410a operates at higher pressures, tougher and more robust air conditioning components are required. Suitable performing components minimize the likelihood of overheating and damaging the machine. It’s not challenging to explain that R410a is dramatically ideal for your home.

For Households, What Does This Mean?

While R22 is still available for the replenishment of older systems with cooling leaks, the cost of this repair has risen dramatically over the last few years.

Can R22 Be Replaced With R410a?

Since R410a needs other air conditioning components other than R22, you can’t refill a device that uses R22 coolant with an R410a coolant, and mixing both coolants can be risky.

In order to benefit from the reliability and performance of R410a, a new system will be mounted. When your air conditioner is approaching the end of its lifespan, the savings of R410a may be a compelling excuse to upgrade the device rather than later in order to reduce the additional expense of fixing R22 refrigerant leaks.

Can You Mix R22 And R410a?

No, you have to start by replacing the R22 condenser with R410a or by an R410a refrigerant.

What Is The R410a Refrigerant Price?

You can get a 25-pound jug for about $70. The types of freon for home ac are either the R22 or the R410a.

Where To Buy R410a Refrigerant.

No one gives a “license” for a particular refrigerant. The EPA accreditation process for the acquisition and managing of hand-picked refrigerants is accessible and is mandatory. R410a is not an exception. Anybody is allowed to buy and store 410a and you can buy it online or through a distributor.

Wait—the Ozone Layer Is Still Declining?

In 1985 scientists reported something very unsettling: They had found a hole in the planet’s ozone layer over Antarctica. The culprits, they said, were humans emitting chemicals that depleted atmospheric ozone above the South Pole and the rest of the globe. Because the ozone layer protects us and other organisms from harmful solar radiation, the international community united in 1987 to sign the Montreal Protocol, which phased out use of such chemicals.

The protocol, widely considered a huge success since its enactment, significantly dropped the level of ozone-depleting chemicals in the atmosphere, and the “hole” over Antarctica has been shrinking. Yet in a new study published in Atmospheric Chemistry and Physics, scientists report that one crucial section of the ozone layer still seems to be declining steadily.

The ozone layer resides in the stratosphere, the region of atmosphere from 10 to 50 kilometers above Earth’s surface. This blanket of gas is vital for life on Earth—it absorbs the sun’s ultraviolet radiation, which can damage DNA and also promote skin cancer and other harm to humans, wildlife and crops.

In reality, ozone is distributed throughout the lower, middle and upper stratosphere as well as in the troposphere, the atmosphere’s bottom layer that extends up from Earth’s surface to about 10 kilometers. Thanks to the protocol, from the late 1990s on, ozone in the stratosphere “looked like it wasn’t going down anymore, which is a massive success,” says William Ball, a researcher in atmospheric physics at ETH Zürich and one of the study authors. But precise measurements of the lower stratosphere have been difficult to make. “One of the key problems that’s been left unresolved is that in the lower stratosphere, there’s lots of variability that we don’t capture in the approach that we typically take to work out what the trends are,” Ball says.

Ball and a team of researchers from institutions around the world wanted to more accurately measure trends in the ozone layer. For their study, they synthesized and then analyzed multiple satellite data sets of atmospheric ozone. The data cover the tropics and mid-latitudes, from 1985 through 2016. The team found ozone in the upper stratosphere has indeed rebounded since 1998. “It’s clear it’s going back up,” Ball says. “This is exactly where we’d expect to see the Montreal Protocol working its best.” They also discovered ozone in the troposphere—which comes in large part from air pollution—rose from 2004 through 2016.

They observed, however, no significant upward or downward trends for the middle stratosphere, or for the total ozone column—the sum of the troposphere and stratosphere—since 1998. Starting in 1985 “you can see [the total ozone column] is going down,” Ball says. “After 1998 we see ozone stop depleting, initially see a slight rise and then it seems to stall.” But the rise was statistically nonsignificant, Ball notes. “What this says is, great, since 1998 ozone hasn’t been depleting any further.” But it also does not appear to be rebounding.

What is the culprit? Ball’s team found the ozone in the lower stratosphere has slowly, continuously dropped since 1998. “We see a small but persistent and continuous decline—not as fast as before 1998 but a continued [trend] down,” he says. “This is surprising, because we would have expected to also see this [region’s ozone] stop decreasing.” The finding is important because the lower stratosphere contains the largest fraction of the ozone layer.

Overall, Ball says, global ozone has declined 5 percent between 1970 and 1998—prior to the protocol’s effect. Since then “our analysis suggests that the [ozone in the] stratosphere has declined…another 0.5 percent, most of which has occurred in the lower stratosphere,” he says. “It doesn’t sound like much, and it’s slower, but it’s contradictory to the trajectory expected in models.”

The research team does not yet know the cause of this persistent decline in lower stratospheric ozone. In their paper they venture a handful of possible explanations, several of which are driven by climate change. Another potential reason might be that rising emissions of short-lived chemicals are reaching the lower stratosphere and destroying ozone. But these are just hypotheses scientists still need to explore. “It’s quite clear that the Montreal Protocol has worked,” Ball says. “But it looks as if something else has come on the stage, and we don’t really know what it is.”

Outside experts are both impressed by the new study and troubled by its findings. “It’s really concerning, because we do not know what’s going on,” says Michaela Hegglin, an associate professor in atmospheric chemistry at the University of Reading in England. “We’re all looking around for signs of recovery, and now this paper comes out and says that the lower stratosphere is declining.”

People should not panic over this new finding, Ball cautions. “At the moment, the [total ozone] column is not getting worse,” he says. But, he adds, “We should be worried. We need to urgently sort this out, because we don’t want the ozone layer to get worse.”

A. R. Ravishankara, a professor in the departments of Chemistry and Atmospheric Science at Colorado State University, says this finding also teaches the world an important lesson. “When you make environmental policies, you study the problem, diagnose, take action—and then most people assume that you’re done. But that’s not the case,” he says. “[You have to] continue to measure and monitor, to make sure that what’s happening is what you predicted. We cannot take our eyes off the ball.”

Hegglin agrees: “The world should realize that the ozone layer story has not ended.”

Check out the whole article here.