SIC 7533 Auto Exhaust System Repair Shops


SIC 7533

This industry classification includes establishments primarily engaged in the installation, repair, or sale and installation of automotive exhaust systems. The sale of mufflers, tailpipes, and catalytic converters is considered to be incidental to the installation of these products.



Automotive Exhaust System Repair


This industry covers exhaust system repair, which primarily involves the sale, installation, and repair of mufflers, tailpipes, and catalytic converters. It is distinct from businesses engaged in the overall repair of automobiles. Such businesses are primarily categorized in SIC 7532: Top, Body, and Upholstery Repair Shops and Paint Shops and SIC 7538: General Automotive Repair Shops. Businesses engaged in specialized automotive repair, such as fuel service, brake repair, and wheel alignments, are classified in SIC 7539: Automotive Repair Shops, Not Elsewhere Classified.

Car exhaust system service is typically provided by dealership garages and auto exhaust repair shops. Besides the existence of numerous "mom and pop" auto service businesses, the industry was led by a few relatively well-known repair shop chains, such as Monro, Midas, and Speedy International. Combined, the 8,000 establishments in the U.S. earned $1.9 billion in 2006 revenue, employing 29,000 people.

Exhaust Systems

The exhaust system of every modern automobile requires frequent care and repair. Condensation in the typical exhaust flow, coupled with ordinary wear, will often result in the necessary replacement of the car's muffler and exhaust pipes. The result is a vehicle with minimal engine noise and an exhaust system that more effectively funnels toxic fumes produced by the vehicle away from the car's interior. When owners determine that their exhaust systems may need repair, they typically avoid do-it-yourself (DIY) replacements and seek the services of exhaust system repair shops. These repairs are also necessary for the owner to maintain car emissions that meet Environmental Protection Agency (EPA) standards. Auto exhaust repair shops install, repair, and inspect the proper pollution control devices.

A car's exhaust system consists mainly of an exhaust pipe, a muffler, and a tailpipe. The exhaust pipe collects the exhaust of a car through a series of exhaust ports in the internal manifold of a car engine. This exhaust is funneled to a downstream pipe and moved through the muffler. The tailpipe discharges the car's exhaust into the atmosphere after it has passed through the muffler.

The muffler is the main component of the exhaust system. It is basically a device that reduces the noise produced by the movement of gas and internal combustion of the car's engine. The typical shell of an automobile muffler is shaped like an oval that measures roughly 20 inches long, 10 inches wide, and 6 inches high. Its internal architecture is made of perforated steel tubes and a number of chambers separated by steel partitions. This combination of filters and tubes acts as a honeycomb that acoustically filters the exhaust sound. The typical muffler can reduce the sound pressure of a car's exhaust from 90 to 60 decibels, a 1,000-fold decrease. More expensive dual exhaust systems have four or more mufflers.

Federal regulations require that motor vehicles be fitted with emissions control devices. Therefore, a mechanism such as a catalytic converter has become an addition to a car's exhaust system. Since their initial requirement in 1975, catalytic converters have served to reduce harmful exhaust. Improved emissions allow the owner to comply with standards mandated by the Environmental Protection Agency.

Legislation to control automobile pollution is in the Clean Air Act, which was passed in 1956 with significant amendments in 1970 and 1977. Regulation of mobile pollution sources was considered controversial. In fact, an EPA...

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