Microbe of the Month: Cladosporium

Microbe of the Month: Cladosporium

Classification Type: Fungi

Cultured from / Found in HVAC: Coiling Coils, Diffusers, Grilles, Filters, Drain Pans, Humidifiers

Noted Health Risks: Fungal Sinusitis, Asthma Attacks, Lung Infections, Chronic Migraines / Fatigue.


About the Cladosporium Fungi

Cladosporium is among the most widespread varieties of mould that can be found in HVAC Systems. Its presence is indicative of high moisture levels and poor Indoor Air Quality (IAQ). Cladosporium is highly allergenic and can reduce occupants' health and overall quality of life. It is dangerous and can spread throughout buildings rapidly. Quickly identifying and removing this type of mould from commercial and residential buildings is of the utmost importance.

This genus of fungi is prevalent both indoors and outdoors, with hundreds of Cladosporium varieties, all of them are harmful to humans. Once indoors, the negative health impacts of Cladosporium intensify, as its concentration in the air will be much higher than outside. Poor ventilation and high humidity levels contribute to its growth, which can be found in many areas throughout the built environment, including walls, ceilings, and soft furnishings.

It tends to grow in colonies/clusters and will have a powdery or velvety texture to it. Like most moulds, Cladosporium can be difficult to identify. The only way to know for certain is to have it sampled by an IAQ expert and then tested by NATA accredited laboratory.


The four most common species include: [2]

  • Cladosporium herbarum. An exceedingly common organism, found on dead herbaceous and woody plants, textiles, rubber, paper, and foodstuffs of all kinds. Indoors, it is found in floor, carpet and mattress dust; damp acrylic painted walls, wallpaper; HVAC insulation, filters and fans. Cladosporium herbarum is frequently by far the most prominent mould in air-spora. It grows over a wide range of temperatures, and has frequently been reported causing spoilage of meat in cold storage.
  • Cladosporium sphaerospermum. This frequently encountered species has been isolated from air, soil, gypsum board, acrylic painted walls, painted wood, wallpaper, carpet and mattress dust, HVAC fans, wet insulation in mechanical cooling units, foodstuffs, paint and textiles.
  • Cladosporium cladosporioides. A cosmopolitan species which has been isolated from meat, soil, air, textiles and paint.
  • Cladosporium macrocarpum. A cosmopolitan species which has been isolated from dead plants, soil, indoor air, apple juice concentrates and seeds.

Prolonged exposure could cause more significant, long-term health issues, including chronic fatigue and chronic migraines

Associated Health Risks of Cladosporium

Species of Cladosporium are not human pathogens except in some cases of immuno-compromised patients. However, Cladosporium species have the ability to trigger allergic reactions to sensitive individuals. Prolonged exposure to elevated spore concentrations can elicit chronic allergy and asthma. Concentrations of 3000 Cladosporium spores per cubic metre of air are generally taken as the threshold concentrations for clinical significance

Symptoms of Cladosporium mould exposure include:

  • Runny nose
  • Itchy eyes
  • Coughing
  • Sneezing
  • Wheezing 
  • Difficulty breathing 
  • Increased allergy symptoms
  • Aggravated asthma symptoms
  • Dizziness/lightheadedness 
  • Headaches

Long-Term Health Impacts of Cladosporium

Prolonged exposure could cause more significant, long-term health issues, including: [1]

  • Allergic fungal sinusitis 
  • Serious asthma attacks
  • Development of asthma in children or healthy adults 
  • Chronic migraines
  • Fungal lung infections
  • Chronic fatigue

Regular detection, quantification and characterisation of moulds in living and working environments are essential for exposure risk assessment to safeguard public health. Thus, monitoring Cladosporium spore concentration in indoor environments is important for Indoor Air Quality control.

Safe indoor air from a serviced HVAC system means a lower particle count and less breathing difficulties for occupants of the building. Clean-Air are IICRC mould remediation experts with the knowledge and experience to test, treat and eliminate serious mould-related risks within your HVAC system. If you have concerns about the air you are breathing, or would like an HVAC health check, contact our team today.