DG Cities, based in London, United Kingdom (UK), is at the forefront of urban innovation. They are an urban innovation company specializing in the integration of ‘smart city’ technologies and approaches to maximize their benefits for cities, and optimize the use of resources, infrastructure and services.

DHD Cooling offers a full service capability to the manufacturing, HVAC, thermal power plant, industrial and chemical industries, offering a bespoke service tailored to one’s exact cooling tower system requirements.

DHL Group is the world's pioneer logistic company. The DHL Group connects people and markets and is an enabler of global trade. It aspires to be the first choice for customers, employees and investors worldwide. To this end, the Group focuses on growth in its profitable core logistics businesses and accelerating the digital transformation in all business divisions.

Founded in 1988 with offices in Kansas City, Austin and Denver, Dialectic is a non-traditional mechanical, electrical and plumbing engineering firm that brings buildings to life. With deep expertise in a range of verticals – including distribution, cannabis, multifamily, senior living and retail/restaurants – they know that true success comes with partnering as an extension of the team.

Digi-Key is one of the fastest-growing distributors of electronic components in the world. Digi-Key offers the world’s largest selection of electronic components in stock and available for immediate shipment. From prototype to production, they are here to fuel innovation all over the world.

Digital Twin Consortium is a global ecosystem of users ,who are driving best practices for digital twin usage and defining requirements for new digital twin standards. It coalesces industry, government and academia to drive consistency in vocabulary, architecture, security and interoperability of digital twin technology. It advances the use of digital twin technology from aerospace to natural resources.

Dimplex offers a variety of both indoor and outdoor electric heating solutions that are attractive in design, as well as powerful in performance. The heaters range from fan-forced to infrared and are suited to different spaces requirements. Dimplex electric fireplaces lead the industry with flame effect technology and realistic media bed accessories.

Direct Expansion Solutions (DXS) specializes exclusively in variable refrigerant flow (VRF) air conditioning and heating systems. That means the entire team – from design engineers to technicians to trainers – are equipped to help one realize the benefits of installing a VRF system on their next project.

Since their company's beginning in 1946, they have been dedicated to providing exceptional service and superior heating, ventilation and air conditioning service and systems to East Texas residents at home and work. Customer satisfaction is their #1 priority.

dmg events is an international exhibition and publishing company with events across more than 25 countries in the Middle East, Europe, Africa, the Americas, and Asia. Headquartered in Dubai since 1989, it has expanded operations from this global hub city to Saudi Arabia, Singapore, Canada, South Africa, Egypt, and the UK, achieving impressive growth in emerging and mature markets.

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.

Dogu Air Conditioning (DOGU Iklimlendirme) started manufacturing ventilation and air conditioning equipment in Izmir, Turkey, back in 1999. It also manufactures Air Handling Units (AHUs), Rooftop Packaged Air Conditioning Units (Rooftop), Heat Recovery Devices, Air Distribution Equipment, and Kitchen Ventilation Devices according to European norms.

Domus Ventilation is an innovator when it comes to supplying the Merchant and Electrical Wholesale industry with value-added products, such as unique 'house packs'​ with pre-determined duct kits, extract fans, and a choice of terminals. Our dedicated design team also offers free-of-charge CAD and Revit designs to illustrate custom ventilation systems that meet the latest building regulations and ensure optimum performance.

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.

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.

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.

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.

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.

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.

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.

Dunster Heat is based in the South West and is a nationwide biomass supplier and installer of vigas wood burning boilers and Akvaterm accumulators. Their biomass systems are combined to form an efficient biomass central heating system.