Carpet Cleaning

The Power of Professional Cleaning: Truck-Mounted Systems

The most effective method for deep cleaning carpets is hot water extraction, often incorrectly referred to as "steam cleaning." The most powerful machines for this process are truck-mounted carpet cleaning units. These are far superior to portable machines and are a critical tool for improving IAQ.

Truck-Mounted System Technology:

• Heat: These machines produce incredibly hot water, which is critical for breaking down soils and killing germs. 

  1. Fuel-fired units use liquid propane or kerosene/diesel to generate heat outputs exceeding 250,000 BTU/hr. 

  2. Heat exchanger units use the engine's heat from its coolant or exhaust, often with an additional heat exchanger that recovers heat from the vacuum blower, to produce a minimum of 70,000 BTU/hr. 

While water has a normal boiling point of 212°F, the high pressure (typically over 100 PSI) of these machines raises the boiling point, allowing the water to stay in a liquid state until it is released from the spray jets. The "steam" you see is actually fog, as the superheated water rapidly cools and condenses when it hits the cooler air. The temperature at the spray jets is about 30 degrees cooler than it is at the machine, and it cools another 10 degrees per inch as it travels to the carpet, so the carpet itself rarely exceeds 160°F, before quickly returning to room temperature.

• Pressure & Flow: Truck-mounted pumps deliver a high volume of water, typically between 3 and 8 gallons per minute, at pressures ranging from 250 to 1000 PSI. This powerful flow  rapidly flushes out contaminants. However, professional cleaners know not to exceed 550 PSI on carpet, as this can drive water too deep to be effectively removed by the vacuum.

• Vacuum: This is the most significant advantage. Truck-mounted machines use a positive displacement vacuum blower capable of producing between 285 CFM and over 800 CFM of airflow, with a vacuum lift measuring between 12 to 16 inches of Hg. CFM (cubic feet per minute) is the volume of air that carries the soiled water, while lift is the pulling force that lifts the water from the carpet into the airflow. This powerful combination ensures deep cleaning and rapid drying. The parasitic load created from the vacuum lift on heat exchanger units also increases the engine's heat output, making the cleaning even more effective.

The Problem with Portable Machines

Portable carpet cleaning machines are generally insufficient for a true IAQ improvement. Their heating elements are generally weak (at best 5,100 BTU/hr), providing water temperatures that rarely exceed a consistent 190°F. Their water pumps provide much lower pressure and flow (0.5 to 2 gallons per minute), which means they cannot efficiently rinse the carpet. Most critically, their use of centrifugal vacuum motors produce often less than 200 CFM with a weaker lift (8-10 inches of Hg). The vacuum exhaust from these portables often vents directly back into the room, which may redistribute the very particulate matter we are trying to remove. This can in some situations worsen air quality instead of actually improving it.

Key Considerations for IAQ-Focused Carpet Cleaning

• Pre-Vacuuming is a Must: All carpet intended for cleaning must be thoroughly vacuumed with a professional-grade vacuum that has a sealed HEPA filter. A sealed HEPA filter ensures that no contaminated air bypasses the filter, protecting indoor air quality. It is far easier to remove dry soil from carpet than after it's turned to wet mud.

• Preventing Mold Growth: Any hot water extraction system can leave too much moisture behind if the machine is not well-maintained or if the technician isn't skilled. This can lead to slow drying times and potential mold growth. After cleaning, professional cleaners must use air movers (blowers) to circulate air over the carpet and ensure it dries quickly.

• The Right Tool for the Job: A common misconception is that using smaller spray jets on the cleaning wand will use less water and lead to faster drying. In reality, smaller jets often require the technician to make more passes, which uses more water overall to effectively remove the soil. The slower water flow can also cause the water to cool before it even reaches the carpet. The spray jets must be correctly matched to the machine's vacuum and heating capabilities for the best results. The manufacturer typically includes spray jets in the carpet cleaning wand that are sized to the machine to produce the highest spiked temperatures at the machine, versus the highest sustained temperatures at the wand.

The Limits of Cleaning to the Surface

It's essential to understand that carpet cleaning is a surface-level process. The carpet assembly itself is a complex structure made up of several layers: the face fibers (what we see and walk on), the primary backing (which holds the fibers in place), a layer of adhesive, and the secondary backing (which provides rigidity and is attached to the subfloor with tackless strips). The only part that is actually being cleaned are the face fibers. While increasing the pressure on a carpet cleaning wand can force cleaning solution beyond the face fibers, no amount of pushing or vacuuming will be able to retrieve that water once it is below the secondary backing. This can lead to over-wetting the carpet pad and subfloor, potentially creating a significant moisture issue and a perfect environment for mold growth.