Negative Pressure Fan, Induced Draft Fan & Blower: What’s the Difference?
Many buyers confuse negative pressure fans, induced draft fans and blowers during procurement. Improper model selection may lead to insufficient pressure, air flow attenuation, equipment corrosion or insufficient suction. These three types are not classified by internal structure. The core distinction lies in their installation position in the system, airflow direction and functional role. We will break down their working principle, pressure range, applicable scenarios, pros and cons to help you select correctly.
1. Core Definition & Fundamental Differences
- Blower (Positive Air Supply, Roots Blower belongs to this category) The blower is installed at the front of the air source. It pumps air into the system and delivers positive pressure, forcing gas into pipelines or reaction tanks. Pressure range: Low-pressure centrifugal blowers work at several kPa. Mingtian Machinery Roots blower single-stage boost: 9.8~98kPa, two-stage series connection can reach up to 196kPa.
Standard specification: Our Roots blowers are manufactured in accordance with JB/T 8941.1-2014 General purpose Roots blowers Part 1: Technical requirements, whose technical indicators are equivalent to ISO/TC117 international blower specifications. Performance test follows JB/T 8941.2-2014. Parameters can be shown in metric units (kPa, m³/min) and converted to imperial units (PSI, CFM) for overseas projects.
- Induced Draft Fan (Negative pressure suction + slight positive pressure discharge) The induced draft fan is mounted at the end of the whole process system. It extracts flue gas and waste gas from furnaces or reaction tanks, forming negative pressure inside the system, then discharges gas outwards. Medium characteristics: Mostly carries dust and high-temperature flue gas (boiler, incinerator waste gas). The impeller requires good wear resistance and high-temperature resistance. It generally runs at low pressure for flue gas exhausting and waste gas collection.
- Negative Pressure Fan (Pure negative pressure air extraction) A negative pressure fan extracts air from an enclosed space to form internal negative pressure, so fresh outside air flows in naturally. It focuses on large air volume with very low pressure, widely used for workshop ventilation and cooling.
Exclusive practical note rarely found online: Many people think induced draft fan equals negative pressure fan. Negative pressure fans are only for space air exchange. They are not suitable for process pipelines with long pipes and high resistance. Induced draft fans can overcome resistance from pipelines and dust removal equipment to extract dusty flue gas. Blowers deliver positive pressure, ideal for aeration and pneumatic conveying that need to overcome water depth and pipeline resistance.
2. Comparison Table of Parameters & Application Scenarios
| Type | Working Mode | Pressure Feature | Typical Application Scenarios |
| Blower | Positive pressure, pumping air into system | Medium & high pressure, 9.8~196kPa for Roots model | Wastewater aeration, aquaculture oxygenation, electroplating bath stirring, biogas boosting, powder pneumatic conveying |
| Induced Draft Fan | Extract gas at system end, exhaust flue gas & waste gas | Low pressure, overcoming resistance of flue and dust collector | Boiler smoke exhaust, incineration waste gas extraction, tail gas extraction for dust removal, VOC waste gas collection |
| Negative Pressure Fan | Extract air from space, create indoor negative pressure | Ultra-low pressure, large air volume | Workshop ventilation & cooling, greenhouse air exchange, livestock farm exhaust |
✅ Quick Selection Guide
- Need to push air into tanks or pipelines → Choose blower (Roots blower preferred)
- Need to extract dusty / high-temperature flue gas from boilers & equipment, then discharge after dust removal → Induced draft fan
- Only large-area ventilation and cooling for workshops, no long-distance gas pipeline transportation → Negative pressure fan
3. Common Selection Misunderstandings
Mistake 1: Trying to use negative pressure fan for fish pond aeration. Negative pressure fan has extremely low pressure and cannot overcome water resistance. Air cannot be delivered underwater, and oxygenation will fail. Aeration projects must adopt blowers.
Mistake 2: Directly use Roots blower to extract waste gas. Roots blowers suit clean or low-dust media. Heavy dusty high-temperature flue gas will quickly wear the Roots impeller and damage equipment. Induced draft fan is recommended for this condition.
Mistake 3: Induced draft fan and negative pressure fan are interchangeable. Induced draft fan can handle pipeline resistance, while negative pressure fan only works for open space ventilation. Air volume drops sharply once long pipelines are installed.
4. Advantages of Mingtian Machinery (Shangu)
- Our Roots blowers are equipped with CNC precision machined impellers. Sealing options include standard, anti-corrosion and explosion-proof types, adapting to wastewater, aquaculture, biogas and chemical media. Single-stage boost 9.8~98kPa, two-stage series up to 196kPa for stable continuous air supply.
- Complete system solutions available: positive pressure air supply and gas conveying package units with silencers, safety valves, filters and pipe fittings for one-stop delivery.
- Professional engineers provide free working condition calculation, distinguish positive/negative pressure working conditions to avoid project rework caused by wrong blower selection. Some previous customers tried negative pressure fans for underwater aeration, and achieved qualified performance after switching to our blowers with our technical evaluation.
- Every unit passes full-load factory test. Overall performance meets JB/T 8941.1-2014. English datasheets and imperial unit conversion are available for overseas clients.
- Complete after-sales service including installation guidance, regular operation & maintenance suggestions, fast supply of original spare parts to reduce production downtime.
Contact Information
Reach us directly：
📞 WhatsApp / Wechat: +86 187 5316 3090
📧 Email: [email protected]
📞 Phone / WhatsApp: +86 187 6611 7068
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🌐 Official Website: https://www.mtrootsblower.com