Dust: How much is too much?

Jul 21, 2020

Dust in a property is normal and inescapable. It may seem that no matter how much you dust and clean, it always seems to build up again. At what point should you be concerned about it? This blog will talk about house dust and how it impacts health and indoor air quality. 

Where Does Dust Come From?

House dust mostly consists of particles from the outdoors, with about one-third of the particles in dust coming from indoor sources such as fabric fibers, human skin cells, insects, and food debris, among others.  Sometimes, clients call when they are concerned about the amount of dust in their property. They will say something like, “I clean my home but the very next day the dust is back!”.  To figure out if there are average amounts in a property versus an excess amount, background information is first collected from the occupant. Pertinent information includes the following: details about construction in the property (or in a neighboring unit if it’s a multi-unit building), recent duct cleaning, any fires in the property or nearby, or recent HVAC maintenance — or lack thereof.  

Construction Dust

If construction was recently completed, there may be residual dust from the work even if the contractor set up containment with plastic sheeting. Cutting drywall and sanding joint compound are just a few examples of activities that could generate small particles that could spill over from the construction area into other parts of the building. The smaller the particles, the longer they may stay airborne and travel farther within the property.

Duct Cleaning

The purpose of duct cleaning is to remove dust and debris from the ductwork and the HVAC system’s air handling unit. In this process, a lot of previously settled dust in the ductwork is loosened and cleaned out.  However, it is possible for some of the stirred-up dust and debris from the cleaning process to float into the living spaces and cause some excess dust accumulation. This may be a short-term increase with possible longer-term decreases in particle levels. There is a certain amount of disagreement regarding the value of air duct cleaning. The EPA website has more information related to duct cleaning.  

HVAC Maintenance

A common problem I see when there is excess dust in a home is the filter attached to the HVAC system. Sometimes property owners forget to change the filter and it no longer is serving much of a purpose. As time goes on, the filter gets clogged and the airlow finds it easier to bypass around the filter. Some systems have electronic air cleaners that need to be cleaned, but are often neglected. Other times, filters don’t properly fit in the rack, which can impact how well particles are removed from the air. 


Fine particles from fires can settle in living spaces and combine with other particles. Nearby wildfires in some parts of the country can add significant amounts of fine particles into the home. Also, wood stoves and fireplaces can contribute to the amount of fine particles in dust. Even small particles from cooking or outdoor vehicle emissions can contribute.

Dead Zone

If there is a particular area in a building that seems to struggle more with dust accumulation than others, it may be due to poor air circulation.  The geometry of a room and the placement of HVAC supplies and returns can impact how air moves in a space. There may be a corner of the room that has very little air movement and a slow air velocity.  When the air slows down, as is common in a corner, the particles suspended in the air will be more likely to settle out via gravity. This area with lower air circulation can be called a “dead zone”.

Dust Levels in the Air

When an occupant sees a lot of settled dust on furniture or other items inside, they may be concerned that they are breathing in a lot of dust or particles. To determine if there are elevated levels of respirable dust in the air, a handheld device called a laser particle counter can be used to measure the number of particles in the air.  Generally speaking, particle sizes of less than 10 micrometers are a concern because they can get into the lungs and cause respiratory health effects. Particle sizes less than 2.5 micrometers are even more concerning with compared to larger-sized particles.


Construction, fire, duct cleaning, or poor HVAC maintenance can impact the amount of dust in a property.  If none of these apply to your property and the space is regularly cleaned, it may be because of a dead zone or it may just be a normal amount.  If you are concerned about the number of respirable dust particles in the air, you can hire Indoor Science to take readings and determine if the levels are elevated in your building. Call us at (312) 920-9393 for a quote for this service!