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Long Island HVAC Service & Repair Experts

Long Island's weather swings—from humid summers to bitter winters—demand a reliable HVAC partner you can count on year-round. Denair HVAC brings over 19 years of expertise in heating, cooling, and emergency repairs across Nassau and surrounding areas. Licensed technicians, free estimates, and same-day service mean your home or business is never left uncomfortable.

Licensed HVAC technician servicing a heating and cooling unit on Long Island

Our HVAC Service & Repair Services

Comprehensive heating, cooling, and ventilation solutions for Long Island homes and businesses—handled by certified technicians.

HVAC Service & Repair

Expert repair and maintenance for all residential air conditioning and heating equipment. Licensed technicians service, maintain, install, and repair AC units, furnaces, water heaters, and ductwork to keep your system running optimally.

24/7 Emergency Repairs

Round-the-clock emergency HVAC repairs with same-day response—usually within 4 hours. Certified technicians arrive fully equipped to diagnose and fix issues on all major brands from 1/2 to 100 tons of cooling capacity.

Preventive Maintenance

Proactive maintenance plans designed to extend system lifespan, reduce energy costs, and prevent surprise breakdowns. Free preventive maintenance for up to 18 months on all new installations, with annual contracts available.

HVAC Installation

Turnkey commercial and residential HVAC installation with end-to-end project management. Includes equipment, ductwork, piping, and controls—delivering projects on time, within budget, and saving clients up to 35% through value engineering.

HVAC System Upgrades

Modernize outdated equipment with targeted retrofits and expert system tune-ups. Optimize performance, enhance comfort, and meet current energy standards without requiring a full system replacement.

Energy Management & Automation

Smart HVAC controls and automation solutions that significantly reduce energy costs and environmental impact—ideal for Long Island property owners seeking lower utility bills and greener operations.

Local HVAC Experts

Reliable HVAC Service Built for Long Island's Climate

Long Island's hot, humid summers and cold winters put serious demands on heating and cooling systems. Denair HVAC's licensed technicians bring over 19 years of hands-on experience servicing all makes and models across Nassau and the broader New York Metro Area. From emergency repairs completed within 4 hours to comprehensive preventive maintenance plans, we deliver upfront pricing, free estimates, and a quality guarantee—so your comfort is never compromised, no matter the season.

Denair HVAC technician performing a service check on a residential HVAC system on Long Island
Trusted By Many

Success Stories

See how Long Island homeowners and businesses have benefited from Denair HVAC's expert service and repairs.

"Denair is the most dependable HVAC service company in New York!"

Christian Taghoy
Christian Taghoy

"I recently used Denair for some repairs to my small two-story office building, and I have to say they are the most honest, hard-working and value focused HVAC provider I have ever experienced! Not only was the price competitive, but more importantly they helped reduce my energy costs from an..."

John Green

"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."

Julian Rodriguez
Julian Rodriguez

"Crew was respectful, fast, and left our place spotless. Five stars."

Jorge S.

"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."

Jackie C
Jackie C

"Great reliable HVAC company, a very rare thing to say these days — the pricing is very competitive and the work is reliable. The staff is professional and courteous, they clean up after themselves and always answer. I would recommend them!"

Yarik Didenko
Yarik Didenko

"These guys are the best. Installed my central air condition. They are quick, thorough and honest! I definitely recommend them."

Nick Garcia
Nick Garcia

"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."

Ken Lucky

"Great company, our office was getting hotter by the minute. Denair had a tech on site with in the hour and the ac working perfect in two hours"

Tanya Gur
Tanya Gur

"Dennis was always available when I called on him. Never was any additional work generated on any quote/contract awarded. Reliable, expert and a pleasure to work with. A real value!"

Al Neese RAM-ARM

"Impeccable install. You can tell they're pros the moment they walk in."

Michael R.

"What a great service. I randomly called to get multiple system inspected in my building. They came on time, done a great job and provided a detailed report. I love their transparency."

Freeman TV
Freeman TV

"They have the best Engineering Service I have ever seen; they are always available on request and perform the maintenance in the most efficient way. Great Service."

Amanda Ron

"Amazing HVAC vendor who is doing multiple accounts for my company."

Mike Kolen
Mike Kolen

"excellent work and quality"

Hagar Sror
Hagar Sror

"Denair is the most dependable HVAC service company in New York!"

Christian Taghoy
Christian Taghoy

"I recently used Denair for some repairs to my small two-story office building, and I have to say they are the most honest, hard-working and value focused HVAC provider I have ever experienced! Not only was the price competitive, but more importantly they helped reduce my energy costs from an..."

John Green

"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."

Julian Rodriguez
Julian Rodriguez

"Crew was respectful, fast, and left our place spotless. Five stars."

Jorge S.

"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."

Jackie C
Jackie C

"Great reliable HVAC company, a very rare thing to say these days — the pricing is very competitive and the work is reliable. The staff is professional and courteous, they clean up after themselves and always answer. I would recommend them!"

Yarik Didenko
Yarik Didenko

"These guys are the best. Installed my central air condition. They are quick, thorough and honest! I definitely recommend them."

Nick Garcia
Nick Garcia

"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."

Ken Lucky

"Great company, our office was getting hotter by the minute. Denair had a tech on site with in the hour and the ac working perfect in two hours"

Tanya Gur
Tanya Gur

"Dennis was always available when I called on him. Never was any additional work generated on any quote/contract awarded. Reliable, expert and a pleasure to work with. A real value!"

Al Neese RAM-ARM

"Impeccable install. You can tell they're pros the moment they walk in."

Michael R.

"What a great service. I randomly called to get multiple system inspected in my building. They came on time, done a great job and provided a detailed report. I love their transparency."

Freeman TV
Freeman TV

"They have the best Engineering Service I have ever seen; they are always available on request and perform the maintenance in the most efficient way. Great Service."

Amanda Ron

"Amazing HVAC vendor who is doing multiple accounts for my company."

Mike Kolen
Mike Kolen

"excellent work and quality"

Hagar Sror
Hagar Sror

"Denair is the most dependable HVAC service company in New York!"

Christian Taghoy
Christian Taghoy

"I recently used Denair for some repairs to my small two-story office building, and I have to say they are the most honest, hard-working and value focused HVAC provider I have ever experienced! Not only was the price competitive, but more importantly they helped reduce my energy costs from an..."

John Green

"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."

Julian Rodriguez
Julian Rodriguez

"Crew was respectful, fast, and left our place spotless. Five stars."

Jorge S.

"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."

Jackie C
Jackie C

"Great reliable HVAC company, a very rare thing to say these days — the pricing is very competitive and the work is reliable. The staff is professional and courteous, they clean up after themselves and always answer. I would recommend them!"

Yarik Didenko
Yarik Didenko

"These guys are the best. Installed my central air condition. They are quick, thorough and honest! I definitely recommend them."

Nick Garcia
Nick Garcia

"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."

Ken Lucky

"Great company, our office was getting hotter by the minute. Denair had a tech on site with in the hour and the ac working perfect in two hours"

Tanya Gur
Tanya Gur

"Dennis was always available when I called on him. Never was any additional work generated on any quote/contract awarded. Reliable, expert and a pleasure to work with. A real value!"

Al Neese RAM-ARM

"Impeccable install. You can tell they're pros the moment they walk in."

Michael R.

"What a great service. I randomly called to get multiple system inspected in my building. They came on time, done a great job and provided a detailed report. I love their transparency."

Freeman TV
Freeman TV

"They have the best Engineering Service I have ever seen; they are always available on request and perform the maintenance in the most efficient way. Great Service."

Amanda Ron

"Amazing HVAC vendor who is doing multiple accounts for my company."

Mike Kolen
Mike Kolen

"excellent work and quality"

Hagar Sror
Hagar Sror
The Denair Difference

Why Choose Denair HVAC?

From Nassau to Brooklyn, here's what sets Denair HVAC apart from the competition on Long Island.

Same-Day Service

Our technicians respond to Long Island service calls usually within 4 hours, any day of the year.

Licensed & Certified

OSHA-certified, manufacturer-trained technicians who meet New York's stringent HVAC licensing standards.

Upfront Pricing

Free estimates with fixed proposal pricing—all unintended costs are absorbed at our expense, never yours.

Nassau Area Coverage

Serving Nassau, Queens, Brooklyn, and greater Long Island with a dedicated team of 28 experienced professionals.

Meet the Denair HVAC Team

Experienced professionals dedicated to keeping Long Island comfortable year-round.

Dennis Cherniy, Founder and CEO of Denair HVAC

Dennis Cherniy

Founder & CEO

Dennis founded Denair HVAC in March 2007 with a single used truck and a vision to deliver honest, affordable HVAC service across New York. With over 17 years of hands-on industry experience, he has grown the company from a one-man operation into a $2M+ revenue enterprise recognized by Inc. 5000 as one of America's fastest-growing companies. Dennis leads Denair's strategic vision, driving the team's culture of transparency, commitment, and client-first service that Long Island and New York Metro customers rely on every day.

Thomas Mishakin, Service Manager at Denair HVAC

Thomas Mishakin

Service Manager

Thomas leads Denair HVAC's service operations across Long Island and the New York Metro Area, ensuring fast response times, efficient technician scheduling, and consistent service quality on every job. He coordinates field teams and customer communication to minimize downtime and deliver a seamless experience from the first call to final sign-off. Thomas's operational focus is what drives Denair's ability to respond to emergency HVAC calls usually within 4 hours—keeping homes and businesses comfortable no matter the season or the urgency of the situation.

Ramil Nurkaev, Application Engineer at Denair HVAC

Ramil Nurkaev

Application Engineer

Ramil designs and supports HVAC systems tailored to each building's unique performance and energy efficiency needs across Long Island and New York. He oversees equipment selection, technical planning, and application support to deliver code-compliant solutions that maximize reliability and minimize long-term operating costs. Ramil's engineering expertise ensures that every installation and upgrade recommendation is backed by precise technical analysis—whether it's a single-family Nassau home or a large commercial property—resulting in systems that deliver lasting comfort and measurable energy savings.

Farrukh Kasimov, Lead Estimator at Denair HVAC

Farrukh Kasimov

Lead Estimator

Farrukh has been a cornerstone of Denair HVAC since 2010, bringing deep expertise in bid preparation and cost estimation to every project the company undertakes on Long Island and throughout the New York Metro Area. As Lead Estimator, he is responsible for delivering comprehensive, timely proposals and tracking opportunities with vendors, subcontractors, and clients. His meticulous approach to value engineering has been instrumental in saving Denair clients hundreds of thousands of dollars on HVAC installations—ensuring competitive pricing without compromising on quality or compliance.

Frequently Asked Questions

What is a Reznor heater?

A Reznor heater is a brand of commercial and industrial gas-fired unit heaters widely used in warehouses, garages, and large facilities. They are known for their durability and efficient forced-air heating output. Denair HVAC technicians are trained and certified by major manufacturers and can service, repair, or replace Reznor heating units across Long Island and the New York Metro Area.

How quickly can Denair HVAC respond to an emergency repair on Long Island?

What types of HVAC systems do you service on Long Island?

Does Denair HVAC offer free estimates for Long Island service calls?

What preventive maintenance plans are available for Long Island homeowners and businesses?

Are Denair HVAC technicians licensed and certified in New York?

How much can I save on a new HVAC installation through Denair's value engineering?

What warranty coverage does Denair HVAC offer on new equipment?

Still Have Questions About Your HVAC System?

Speak with a Long Island HVAC expert today—consultations and estimates are always free.

Our Long Island Service Areas

Denair HVAC proudly serves Long Island and the wider New York Metropolitan Area with fast, reliable HVAC service.

11+ Regions

Service Area

24/7 On Call

Emergency Availability

4.7★ Rated

Customer Rating

Do We Service Your Long Island Location?

Contact us to confirm coverage in your area and get a free same-day estimate.

Certified & Trusted

Awards and Recognition

Inc. 5000 award logo recognizing Denair HVAC as one of America's fastest-growing companies

Inc. 5000 Recognition

Named one of America's fastest-growing companies.

OSHA 40-hour certification badge for Denair HVAC technicians

OSHA 40-Hour Certified

All technicians hold OSHA safety certification.

New York Registered Mechanical HVAC Contractor license badge

Registered HVAC Contractor

New York State licensed mechanical contractor.

Get Fast, Reliable HVAC Service on Long Island Today

Fill out the form below and a Denair HVAC specialist will reach out promptly to schedule your free estimate or same-day service call. No obligations, no hidden fees—just expert HVAC help when you need it most.

Contact Us Today

For immediate assistance, feel free to give us a direct call at 718-791-5074 You can also send us a quick email at