Incorrect Statement:
Fabric filters have low efficiency in comparison to venturi scrubber.

Explanation:
Fabric filters, also known as baghouses, are air pollution control devices used to remove particulate matter from industrial gases. They are widely used in various industries such as power plants, cement plants, steel mills, pharmaceuticals, and many others. Fabric filters are highly efficient in removing small particles and have several advantages over other air pollution control devices.

Advantages of Fabric Filters:
- High Particle Removal Efficiency: Fabric filters are capable of removing very small particles from the gas stream, including submicron particles. They can achieve high collection efficiencies, typically greater than 99% for particles larger than 1 micron.
- Chemical Resistance: Fabric filters are generally resistant to chemical attack. They are designed to withstand a wide range of corrosive and abrasive gases and particulates. The filter media used in fabric filters are selected based on the specific chemical properties of the gas stream.
- Large Gas Handling Capacity: Fabric filters can handle large volumes of gas at relatively high speeds. They have a high gas-to-cloth ratio, which means that a large amount of gas can pass through a given area of filter media. This allows for efficient operation and high throughput.
- High Collection Efficiency: Fabric filters can achieve collection efficiencies as high as 99.9% for particles larger than 0.3 microns. The collection efficiency depends on several factors such as the type of filter media, particle size distribution, and gas velocity.

Comparison with Venturi Scrubber:
Venturi scrubbers are another type of air pollution control device that uses a high-velocity liquid spray to remove particulate matter from the gas stream. While venturi scrubbers are effective in removing particles, they have certain limitations compared to fabric filters.

- Venturi scrubbers are generally less efficient in removing small particles compared to fabric filters. They are more effective in removing larger particles, typically above 10 microns. Fabric filters, on the other hand, can capture particles as small as submicron size.
- Venturi scrubbers may also have limitations in handling high gas volumes at high speeds. Fabric filters, with their large gas handling capacity, are better suited for applications with high gas flow rates.

Therefore, the incorrect statement is option C: "They have low efficiency in comparison to venturi scrubber." Fabric filters actually have high efficiency in particle removal and are preferred in applications where small particle capture and large gas handling capacity are required.