This is a result of a projected rebound in consumer spending on durable goods and in residential construction spending, which both suffered during the 2007-2009 recession, says The Freedonia Group, Inc in its Consumer Water Purification & Air Cleaning Systems study.
Consumers will also have increasing concerns about the quality of the air and water in the home and increased awareness of the health and aesthetic benefits of these systems, it suggests. In general, the market size will depends on the quality, or the perceived quality, of local tap water supplies.  
Water purification systems incorporating conventional filtration media accounted for the majority of demand for water systems in 2009, with 76% of sales value. Faster growth will be registered by higher-value reverse osmosis and distillation systems. 
In 2009, point-of-use (POU) systems, which are installed at a single outlet, had the larger share of demand for water purification systems and sales of these types of systems are expected to grow faster through 2014, albeit from a very low base, due in part to the rebound of single family home construction. 
Among air cleaners, conventional filtration systems accounted for the largest share of value demand with 47% in 2009, while electrostatic air cleaners, which often operate more quietly and efficiently, are projected to achieve faster gains through 2014. Portable air cleaners accounted for the larger share of air cleaner sales in 2009 and sales of the cleaners are expected to continue to grow at a rate faster than that of whole-house air system sales.