Donaldson Company helps solve some of the world's most complex filtration and contamination control challenges, and is one of the largest global providers of unique filtration technologies and high-quality filters and parts. Their filtration technologies and products are used every day, in a variety of industries and environments, including aerospace, agriculture, construction, manufacturing, mining, power generation, transportation, etc.

Done-Rite Plumbing & Rooter is the premier plumbing company in Orange, California, USA. They are a full-service plumbing contractor offering everything from water heater installation & repair, drain cleaning sewer line repair & installation, and general plumbing services. They service the entire Orange County area and can be out to any property in the area same-day for plumbing services.

Dongfang Electric Corporation (DEC) is a company based in Chengdu China, with businesses all over the world. With a long-term commitment to providing an integrated solution to global energy, transportation, environmental protection, and other infrastructure, they are determined to become top-notch energy and electromechanical equipment system integrator, service provider, engineering contractor, and overseas infrastructure investing.

Donnelly is the most reliable mechanical contractor in New York City. Donnelly gives the clients peace of mind. Donnelly does this by providing the most innovative services and solutions through the experienced team. New York City’s premier provider of HVAC service, maintenance, and construction, as well as energy solutions.

Donovan & Sons, Inc. provides a full range of plumbing, heating, ventilation and cooling services for both residential and commercial customers. The company is made up of 5th generation plumbers and HVAC technicians dedicated to providing their customers with prompt, reliable, professional services.

Dorin is a consolidated industry, known throughout the world and continues to grow. Thanks to the decades-long and ongoing commitment to research, their solutions provide maximum energy saving and efficiency and are designed around the needs of customers,

Dornan Engineering Ltd. offers a full range of Mechanical, Electrical, Instrumentation, HVAC and Commissioning Services that will take any project from the construction drawings right through to final handover and commissioning.

Double Cool supplies and installs a range of refrigeration cabinet, acrylic door solutions throughout the UK. They work with supermarkets, chain and independent convenience stores, petrol stations, farm shops, garden centres and refrigeration engineers to provide a durable, cost saving, energy reducing solution for chiller cabinets.

Doucette Industries is a globally renowned supplier of heat exchangers, vibration absorbers and OEM parts to the HVAC/R industry since 1975. Their extensive products include suction line heat exchangers, heat recovery desuperheaters, coaxial coils, brazed plates, tube-in-tube condensers, shell and tube heat exchangers, vibration absorbers, pool water heat exchangers.

Douglas Cooling & Heating is a full-service HVAC company that serves the higher Birmingham area. They strive hard to provide prompt and efficient solution.

Dowdle Heating and Air has been serving North MS since 1952. In 2012, Chris Powell merged with Dowdle to create Dowdle and Powell Heating and Air. They are an HVAC contractor. They offer service, sales, installation and fabrication of all HVAC equipment including air conditioners, thermostats, heat pumps, air filters, gas furnaces, programmable thermostats, humidifiers, ductless split systems.

Dowling Corporation is a pioneer HVAC/R mechanical services provider serving clients in New Hampshire, Southern Maine, and the North Shore of Massachusetts. Providing comfort and peace of mind since 1961.

DP-Pumps develops and manufactures stainless steel centrifugal pumps and pressure boosting systems for applications involving drinking and process water. They provide Sewage and waste water pumps, Hydro pneumatic pressure booster systems, Centrifugal pumps, Submersible pumps, Process water pumps, Firefighting pumps and systems, HVAC circulators, and Pressure boosting systems.

dPoint Technologies began in 2005 with a goal to develop membrane-based humidification components for the hydrogen fuel cell industry. In 2008 dPoint expanded its vision and product line to applying the technology developed for the fuel cell industry to manufacture Energy Recovery Ventilator (ERV) membrane and cores for the HVAC industry.

Safe-T-Flush by Drain Shield is the new standard for condensate drain management, preventing leaks and clogs by ensuring a natural flow of condensation out of the drain line. The Safe-T-Flush system eliminates repetitive service calls, improve air quality with the unit, and prevent extensive and costly property damage.

Drake Refrigeration, Inc. is one of the best industrial chiller manufacturers. design custom industrial process chillers to meet a customer's particular .

Drews Marine GmbH supplies the maritime industry with highly individual or standardized solutions in the areas of refrigeration, air conditioning, ventilation, heating, pipeline construction and automation.

Dring Air Conditioning & Heating is a family-owned business which makes them a rare breed in this era of big box stores and Internet commerce. They first opened their doors in 1953, and as their core of loyal HVAC heating and cooling customers has grown, their area of service has expanded.

Dryaire Systems, Located in Germantown, Wisconsin specializes in Commercial, Residential and Grow Room Dehumidification Systems. DryAire Systems is a provider of dehumidifiers - industrial, commercial and residential applications - indoor swimming pools, ice rinks, process water treatment plant, agricultural dehumidification solutions and many more

DT Air Conditioning & Heating is Texas' renowned expert heating and cooling company. They offer furnace and air conditioning services in and around Plano, Texas, USA.

As a pioneer Gas and Heating Company in West Yorkshire, DTR Gas and Heating knows what exceptional and reliable workmanship means. They are providing clients with a wide range of services, all with guaranteed quality and precision. From the beginning stages of the project all the way to the completion of the process, they work side-by-side with clients every step of the way.

Du-Co Ceramics is a technical ceramics manufacturer using steatite, cordierite, magnesium oxide, alumina, mullite and forsterite. Ceramic componants are produced by dry pressing and extrusion methods.

Dual Air Inc. is their local Daikin Sales, Service, and Installation professional heat & air contractor. Servicing all brands of Residential and Light Commercial HVAC and Radiant Heating and Cooling Systems, including Furnace and Air Conditioner Maintenance, Repair, and Replacement for the Twin Cities south of the river area.

Duane Blanton is a trusted expert for comprehensive home comfort solutions, specializing in HVAC services, plumbing, and indoor air quality. From expert HVAC installation and maintenance to water heater repair, drain cleaning, and trenchless sewer repair, they ensure the home's essential systems run efficiently. They also provide advanced water quality solutions, sump pump services, boiler maintenance, and professional duct cleaning.

Ducane is all about providing outstanding value in home heating and cooling. They provide residential heating and cooling products, packaged units, and split systems under 5-tons.

DUCO Ventilation & Sun Control focuses on health in all its developments in the field of ventilation and sun protection systems, always with a nod to optimal occupant comfort and maximum energy efficiency.

Duct & Vent Cleaning of America, Inc. was founded in April of 1989 by Ron Eckman. As early as February of 1990, Duct & Vent Cleaning of America, Inc. joined NADCA, the HVAC Inspection, Maintenance and Restoration Association. In fact, they were the first company to be allowed membership that used portable hepa vacuums in the cleaning process.

Duct Care Inc. provide is providing Professional Duct Cleaning Service since 2008. They also provide Furnace Cleaning, AC Coils Cleaning, Dryer Vent Cleaning and Central Vacuum Cleaning services. Their Unique Duct Cleaning process allow them to meet or exceed NADCA Duct Cleaning Procedure guide lines. From using pressure guns to different snake agitating whips and tools, they aim to not only get the job done, but get the job done right.

For over 30 years, Duct Doctor USA has been providing quality air duct cleaning for both residential and commercial customers. Duct Doctor was founded by a board-certified allergist in 1985 with a mission to improve the air quality of homes and workplaces.

At Duct Hygiene they specialize in the servicing of commercial kitchen extraction systems, fresh air ventilation and Fire Damper Inspection & Testing. They provide maintenance services to both blue chip and private sector clients throughout the UK, performing over 7,500 service visits each year maintaining building safety and compliance.