Forced Air

• Michael Segal MD PhDF says that forced air systems can circulate allergens, exacerbating symptoms of asthma. This is not an issue with steam, or radiator, heating systems.
  
  

Steam Ventilation

• As with any poorly ventilated home, houses that use radiators can harbor some of the same health hazards as those with forced-air systems: dry air, carbon monoxide build-up, dust mites and other environmental allergens.
  
  

Exceptions

• When fitted with an electrostatic precipitator and a high-quality filter to trap particles in the air, a forced-air HVAC system can prevent allergens from circulating through a home and actually improve indoor air quality, according to Consumer Reports.
  
  

Considerations

• A home heated with a radiator can also be safe for asthmatics, as long as air is properly circulated and filtered. Consult an HVAC technician for advice on air circulation and filtration.
  
  

Expert Advice

• Whatever type of HVAC system is in your home, limit exposure to outdoor allergens by keeping doors and windows closed, and regularly washing bedding and window treatments.