24/7 Emergency Repairs
Certified technicians on call around the clock, arriving fully equipped to diagnose and fix urgent HVAC failures — usually within 4 hours — minimizing disruption to your home or business.
When your heating or cooling system fails on Long Island — whether during a frigid January nor'easter or a sweltering August heat wave — Denair HVAC responds fast. Our certified technicians are on call 24/7, typically arriving within 4 hours to restore comfort and protect your home or business from costly downtime. No waiting, no guesswork, just rapid relief.
From same-day urgent repairs to preventive maintenance, we cover every critical HVAC need across Long Island.
Certified technicians on call around the clock, arriving fully equipped to diagnose and fix urgent HVAC failures — usually within 4 hours — minimizing disruption to your home or business.
Complete repair services for all residential and commercial heating and cooling equipment, including AC units, furnaces, water heaters, duct systems, and more — backed by a free estimate.
Proactive maintenance plans that keep your HVAC running efficiently year-round, reduce energy costs, prevent unexpected breakdowns, and extend equipment lifespan with customized service contracts.
Modernize aging equipment with targeted retrofits and expert system tune-ups to improve performance, meet current energy standards, and enhance comfort without full system replacement.
Smart controls and automation solutions designed to significantly reduce energy consumption, lower utility costs, and minimize your environmental impact across residential and commercial properties.
Variable Refrigerant Flow and split system installations ideal for Long Island properties with rooftop or balcony access, delivering flexible, high-efficiency climate control for any configuration.
Reach our Long Island emergency dispatch line any time of day or night. Our service team immediately assesses your situation, prioritizes your call, and dispatches the nearest available certified technician without delay.
See how Long Island homes and businesses count on Denair HVAC when emergencies strike.
"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"
"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..."
"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."
"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."
"Denair is the most dependable HVAC service company in New York!"
"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."
"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!"
"Crew was respectful, fast, and left our place spotless. Five stars."
"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!"
"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."
"Impeccable install. You can tell they're pros the moment they walk in."
"These guys are the best. Installed my central air condition. They are quick, thorough and honest! I definitely recommend them."
"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."
"I didn't even know about their referral program sending DENAIR to one of my commercial tenants. It was a nice surprise to get paid for referral. Based on the tenant's feedback, the job was well-done. Now it's no brainer to recommend DENAIR to all my tenants"
"Amazing HVAC vendor who is doing multiple accounts for my company."
"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"
"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..."
"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."
"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."
"Denair is the most dependable HVAC service company in New York!"
"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."
"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!"
"Crew was respectful, fast, and left our place spotless. Five stars."
"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!"
"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."
"Impeccable install. You can tell they're pros the moment they walk in."
"These guys are the best. Installed my central air condition. They are quick, thorough and honest! I definitely recommend them."
"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."
"I didn't even know about their referral program sending DENAIR to one of my commercial tenants. It was a nice surprise to get paid for referral. Based on the tenant's feedback, the job was well-done. Now it's no brainer to recommend DENAIR to all my tenants"
"Amazing HVAC vendor who is doing multiple accounts for my company."
"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"
"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..."
"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."
"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."
"Denair is the most dependable HVAC service company in New York!"
"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."
"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!"
"Crew was respectful, fast, and left our place spotless. Five stars."
"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!"
"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."
"Impeccable install. You can tell they're pros the moment they walk in."
"These guys are the best. Installed my central air condition. They are quick, thorough and honest! I definitely recommend them."
"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."
"I didn't even know about their referral program sending DENAIR to one of my commercial tenants. It was a nice surprise to get paid for referral. Based on the tenant's feedback, the job was well-done. Now it's no brainer to recommend DENAIR to all my tenants"
"Amazing HVAC vendor who is doing multiple accounts for my company."
We combine speed, expertise, and transparency to deliver emergency HVAC repairs Long Island residents and businesses can rely on.
We arrive at your Long Island property typically within 4 hours, 24 hours a day, 7 days a week.
Every technician is OSHA-certified and manufacturer-trained, ensuring code-compliant repairs on all major HVAC brands.
Fixed proposal pricing means no hidden costs — all unintended expenses are covered at our own expense.
Serving Nassau and the greater New York Metro area since 2007, with 400+ completed projects and Inc. 5000 recognition.
Experienced professionals committed to fast, reliable emergency HVAC service.
Founder & CEO
Dennis founded Denair HVAC in March 2007 — starting with just one man and a beat-up used truck — and has spent over 17 years building it into a recognized leader in the New York Metro HVAC industry. Under his strategic vision, Denair grew from zero to over $2 million in annual revenue within five years and earned a coveted spot on the Inc. 5000 list as one of America's fastest-growing companies. Dennis holds deep expertise across every facet of the HVAC business, from emergency service operations to large-scale commercial installations. His commitment to honesty, speed, and quality has shaped a company culture that Long Island and NYC clients trust when every minute counts.
Service Manager
Thomas leads Denair HVAC's service operations with a relentless focus on fast response times and consistent quality — critical qualities for a team handling emergency HVAC calls across Long Island and the greater New York area. He oversees technician dispatch and scheduling, ensuring that when a system fails at 2 AM in Nassau County, the right certified technician is on the road within the hour. Thomas coordinates seamlessly between field crews and customers, reducing downtime and keeping every service interaction smooth and professional. His operational discipline is a key reason Denair consistently meets its 4-hour emergency response commitment.
Application Engineer
Ramil brings deep technical expertise to Denair HVAC as the team's Application Engineer, designing and supporting HVAC systems tailored to the unique performance and efficiency demands of each Long Island and New York Metro property. From selecting the right equipment for a Nassau County commercial building to ensuring a residential repair meets current energy codes, Ramil provides the engineering backbone that makes every service recommendation reliable and cost-effective. He oversees technical planning, equipment selection, and application support — ensuring long-term reliability, measurable energy savings, and full code compliance on every project Denair undertakes.
Denair HVAC operates 24/7 and typically dispatches a certified technician to Long Island properties within 4 hours of your call. Our service team answers around the clock, including nights, weekends, and holidays, so you are never left waiting during a heating or cooling crisis in Nassau County or the surrounding areas.
Our Long Island HVAC experts are available 24/7 — call us now for immediate assistance.
Denair HVAC provides emergency HVAC repair services across Long Island and the greater New York Metropolitan Area.
Nassau & Beyond
Service Area
24/7, 365 Days
Emergency Availability
Within 4 Hours
Response Time
Call our 24/7 dispatch line and we'll confirm coverage for your address immediately.
Recognized as one of America's fastest-growing companies.
All technicians hold full OSHA safety certification.
Fully licensed Mechanical/HVAC Contractor in New York.
Fill out the form below and our 24/7 dispatch team will contact you immediately to confirm your service call and get a certified technician on the way — typically within 4 hours.
For immediate assistance, feel free to give us a direct call at 718-791-5074 You can also send us a quick email at
For immediate assistance, feel free to give us a direct call at 718-791-5074 You can also send us a quick email at