DNV GL is a global quality assurance, software solutions and risk management company. They provide classification, technical assurance, software and independent expert advisory services to the maritime, oil & gas, power and renewables industries. They also provide certification, supply chain and data management services to customers across a wide range of industries.

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.

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.

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.

Downriver Refrigeration Supply Co. is a renowned full line HVACR (Heating, Ventilation, Air Conditioning, and Refrigeration) distributor in the metropolitan Detroit area of the United States.

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 .

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.

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.

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.

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.

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.

Located in St. Louis, Missori, U.S.A., Ductformer Inc. is a manufacturer of machinery for the Duct Fabrication Industry. They manufacture sheet metal and duct fabrication machinery including rollformers for duct flanges, slip and drive cleats, Pittsburgh, and snaplock seams.

Duke Energy is one of the largest energy holding companies in the United States. Its Electric Utilities and Infrastructure business unit serves approximately 7.5 million customers located in six states in the Southeast and Midwest.

DunAn Sensing offers high-performance OEM pressure sensors, transducers, and transmitters with MEMS packaging technology compatible with harsh media.

Dunphey-Smith takes pride in delivering not only quality service but also the best value and brand names in heating and cooling products.

Duquette Refrigeration has provided commercial refrigeration and HVAC service, installation, and 24/7 emergency repair to businesses throughout New England since 1986.

Dura Products, Inc is a state-of-the art Indiana based manufacturer of metering, pumping and dispensing systems for the DEF, AG, and turf Chemical industries. Founded by owners with decades of knowledge in farming and the chemical sales industry, Dura Products Inc goes beyond excellent design to incorporate innovative, versatile and durable transfer pump solutions with the end consumer always in mind.

Durkee® is a multi-national high-tech enterprise with a focus on offering solutions of high quality elastomeric thermal insulation, customized fabric air ducting and A/C system integration in the HVAC/R industry over the past 25 years.

Duroair has fast become a pioneer in innovative airflow and air filtration technology. Duroair designs and manufactures flexible end-to-end clean air solutions, focusing on (i) painting and coating, (ii) dust and particulate collection, (iii) weld smoke and oil mist collection, (iv) positive and negative pressure clean rooms, (v) environmental isolation rooms and (vi) non-destructive testing applications.

Established in 1995, Dusty Ducts, Inc. is certified as a minority-woman-owned-small business. As a Michigan corporation we provide HVAC Restoration, Indoor Air Quality and Energy Conservation for clients throughout Michigan and across the Midwest United States.

Dynamic Filtration manufactures robust, industrial-grade EDM filters, long lasting cellulose industrial fluid filters and several popular waterjet filters.

Dynatemp International, Inc. is a privately held supplier of refrigerants and refrigerant recovery services. Dynatemp offers the HVAC/R market a portfolio of products, services, and market intelligence that is designed to increase long-term profitability, customer loyalty, and environmental stewardship.

The E.ON Group is one of Europe's largest operators of energy networks and energy infrastructure and a provider of innovative customer solutions for 50 million customers. Thus, they are decisively driving forward the energy transition in Europe and are committed to sustainability, climate protection, and the future of the planet.

Eagle Disinfection is responsible for providing marketing, distribution and customized solutions tailored to the client’s needs and is equipped to facilitate installation and maintenance services on all Puradigm products. Puradigm is the world’s most validated purification technology for combating dangerous surface and air contaminants safely in populated environments 24/7.

Eagle Mechanical, Inc. is a HVAC, plumbing, process and piping mechanical contractor with 30+ years’ experience. They help customers to purchase, install, maintain or replace any heating, air conditioning, refrigeration and plumbing systems. They specialize in industrial and commercial facilities, like hospitals, office buildings, schools, and government facilities.