The Stomata

Skytree’s Stomata reduces the load on a car HVAC system by enabling the recirculation of internal cabin air at the same temperature while maintaining its quality. Effectively creating an indoor air bubble, Stomata also leads to healthier cabin air and longer external air filter lifetimes by reducing the amount pollution introduced into the car cabin, while filtering unhealthy gases such as NOx and SOx.

The significant reduction in load on the HVAC system leads to up to 20% average increase in electric vehicle range. In order to achieve this, Skytree uses a sorbent originally developed at the European Space Agency to recirculate air inside of spacecraft.

Worldwide air quality levels have reached new lows. Asian cities are closing schools and issuing general warnings while in Europe, many cities far exceed EU limits on NOx levels. To exacerbate the problem, air filters in cars are hugely variable in performance with some removing >90% of pollutants and others below 20% [ref].

Electric vehicle range is another area for concern. OEMs see that the advertised range of their model does not hold up in weather extremes, such as deserts or simply snowy environments. With the market penetration of EVs projected to be 20% by 2025 [ref], we see a compelling market for Stomata.

The Stomata

Category: Automotive

In car cabins, there is a rapid build-up of CO2 due to occupants’ exhalation. The CO2 concentration in recirculation mode increases from the ambient level of 400 ppm to 5000 ppm within minutes. Studies show negative effects on cognitive abilities, alertness and concentration levels at high levels of CO2. Additionally, there is considerable buildup of water in closed environments due to human occupation which can quickly cause window fogging.

(Ref: 2017 SAE study on CO2 levels in car cabins:


In traditional HVAC systems, air is brought from outside to flush the indoor air and maintain lower, healthier CO2 & humidity levels. However, the process is energy intensive as the outside air needs to be heated or cooled to match indoor ambient temperature. Traditional HVAC systems can take up to 60% of the energy usage for cars (especially EVs) in colder or hotter temperatures. Additionally, they bring in outside pollution which can be hard to filter and equally unhealthy for passengers, including gases, odours, fine particulates, VOCs & viruses.

Stomata stabilizes CO2 and humidity levels, enabling air to be fully recirculated. The process additionally improves air quality levels by reducing the introduction of outdoor pollution by 80% and allows for multi-pass filtration. As a bonus of both multi-pass filtration and range extension, volume savings are gained through reduced cabin air-filter size requirements and battery volume.

Product Specs

  • Stand-alone volume: 12 litres (incl. full regeneration system)
  • Average power consumption: 350W
  • Noise & Vibration tested


  • Removes CO2 , H2O , NOx , SOx
  • Up to 20%  range increase depending on scenario
  • Reduced HVAC system load
  • Decrease in outdoor pollution by up to 80%
  • Filter lifetime > 1 year
  • Benign non-toxic sorbent
  • Regulates CO2 to maintain CO2 at safe levels < 1500ppm
  • Regulates humidity to maintain reduced to no window fogging
  • Operates at STP

Our Canopy of Services


Your product is unique and has particular requirements, extreme use-cases and base use-cases. Our CO2 & humidity removal process can be tailored to meet the needs of your customer. We'll work closely with your engineering team to develop a product design that suits your specific needs.


Has your institution or company identified a high-potential material for application to CO2-removal? We'd be excited to characterize and compare its performance under real-world conditions as a service we provide.


Our automotive product is available for demonstration at short notice. Is your company/institution keen to develop a product line in a different sector using Skytree’s CO2 removal process? We can develop a feasibility pilot to start a new partnership.