What do Humidifiers do? Dry air can have unhealthy and damaging effects in the home. Many viruses thrive in low humidity, which can increase the likelihood of colds, flu, and other upper respiratory illnesses. Dry air can also aggravate asthma and allergy symptoms. Too low humidity levels can also cause permanent damage to your home, including split or cracked wood floors or trim. Keeping your home’s humidity level at 30% – 45% can help reduce the negative effects of dry air. An Aprilaire Whole Home Humidifier controls the amount of humidity in the air.