If you are experiencing unexplained headaches, a cough and runny nose, dizziness or fatigue with no known culprit, you may want to inspect a common household appliance.
Air conditioning is one of the most popular modern conveniences, protecting against heatwaves and filling homes with cool air.
But, if the units aren't installed, maintained or cleaned properly, they can become rife with mold, inflicting serious health complications on unsuspecting residents breathing in their air.
Tony Abate, an indoor air quality expert and vice president of AtmosAir Solutions, told DailyMail.com: 'Dirty air conditioning units, especially those filled with mold, can certainly impact your health... [and] spread mold and other contaminants within a room.'
In many instances, air conditioning units become contaminated with black mold, which typically grows where there is moisture from water damage, water leaks, condensation or flooding.
The Cleveland Clinic reports black mold triggers an immune response and people may experience exacerbated allergies and develop symptoms like sneezing, coughing, congestion and eye irritation.
Shu Saito, founder and CEO of HVAC and filtration company All Filters, told DailyMail.com: 'Filthy air conditioners and those infested with mold create health hazards primarily from compromised indoor air quality and the unit acting as a continuous source of airborne pollutants.
'If an AC unit is not properly maintained, then dust, dirt, and moisture accumulating on its surface can serve as an ideal setting for mold growth. Once mold has taken hold, spores are released into the air whenever the system is operating and can cause everything from a variety of respiratory problems to skin irritation, increasing the severity of asthma and allergic reactions.'
In many instances, air conditioning units become contaminated with black mold,
He continued: 'These spores, along with other contaminants in the system, such as bacteria and dust mites, may cause problems ranging from minor nasal blockage and sneezing to more serious conditions like bronchitis, chronic coughing, or even sinus infections in people who have compromised immune systems.'
For most people, exposure to black mold will not make you severely ill or cause death.
However, for people with weakened immune systems, black mold exposure can cause mycosis, a fungal infection throughout the body that leads to fatigue, muscle aches, chest pain, weight loss and asthma-like symptoms.
Other types of mold that can commonly grow in air conditioning systems include alternaria (green or brown with a velvet-like texture) and chaetomium (cotton-like appearance with a musty odor).
If mold is growing in your air conditioning, you may notice a musty odor or see black spots around the unit.
If you suspect a contaminated AC unit, you can reach out to specialists to get it tested.
The cost of getting an AC unit tested for contamination can vary depending on the type of test and the system being tested, but RPF Environmental notes the average is around $400.
For those on a budget, DIY test kits are inexpensive ways for inspecting the air quality in your home initially and can range from $15 to $200.
Air conditionings with a build up of moisture, poor ventilation, air vents and ducts growing mold, as well as units that aren't used frequently used can all spread contaminants into the air that people unknowingly breathe in.
Glenn Gault, the CEO at Gault Heating & Cooling, explained: 'What air conditioning units do is pull in air from the room, cool it, and then release it back to the room.
'When air from the room is pulled into the AC unit, it passes through a filter that removes many particles, such as dust and mold spores, before it flows over the cooling coils.
'If there are mold spores growing on the coils or other internal parts of an AC unit, they can be blown out with the air, lowering indoor air quality and posing a huge threat to your health.'
And Mr Saito added: 'These problems worsen in houses or structures that are not well ventilated because these kind of contaminants get trapped indoors and keep on re-circulating.
'Due to this repeated exposure, the membranes of respiratory ways get chronically inflamed, weakening the body's immune response and hence making it more prone to infection.'
Confirming Mr Saito's claims, Autumn Clayman, 29, from California, said mold in her apartment's air conditioning unit left her suffering from 'burning' skin and a bill for $10,000 to replace her belongings and move.
Autumn Clayman claims black mold in her apartment's air conditioning unit caused her skin irritation
She started suffering from a burning sensation around her face and began to see red marks appear on her skin shortly after moving into her new apartment in Los Angeles in February.
She then started developing eczema - chronic inflammation and itchiness of the skin - across her body and her allergies worsened.
Unsure of what was causing her issues Ms Clayman cut out certain foods to see if things improved, but they didn't.
However, Ms Clayman's flare ups got worse and she believed the cause was something in her apartment. So, she stayed at her boyfriend's for two weeks. While there, her symptoms began to ease.
Feeling confident it was her home causing the issues, Ms Clayman paid $780 to have her apartment tested for mold and it came back positive for stachybotrys chartarum - or black mold - in both of her air conditioning units, which had been blasting cold air throughout the apartment.
AC repair outfitter Smedley's says the best way to prevent a build up of black mold in your AC unit is by cleaning the evaporator coil on an annual basis.
The expert cleaners note: 'Enclosed within the air conditioner plenum, the evaporator coil is kept damp and in the dark - the perfect conditions for mold to flourish.'
It is possible to clean the evaporator coil yourself using a mild detergent and warm water, but you 'risk damaging the fragile aluminum fins lining the evaporator coil.'
Therefore, it might be best to get a technician.
Other tips experts offer are to drain and clean the condensate drip tray, change the air filters every three months, and to invest in a stand-alone dehumidifier to help curb mold growth.
They also recommend UV germicidal lamps, which can be installed near the evaporator coil and other places that are a hotbed for mold growth.
Long-term usage of UV germicidal lamps 'not only tackles existing mold growth, but it also plays a role in preventing future mold, mildew, and bacteria growth.'
If the AC unit is beyond saving, it might be worth purchasing a new one, with window, wall mounted and freestanding models available. Prices range from $150 to $600, depending on the offerings.
Overall, Mr Saito stressed proper maintenance of air conditioning units is crucial to maintain both a cool and healthy home: 'Furthermore, mold growth and dust accumulation burden the HVAC system, degrading its performance, which results in high energy expenses.
'The cleaning and replacement of filters in the system on a regular basis are vital not only to keep the systems at work but also to ensure that the health and well-being of all in the environment are protected.'