Based on the dollar volume of the deals announced this year so far, it appears that M&A activity is heading for a record year in 2015. As a long time market watcher and investor, this is a major “watch out” item for me because this sort of deal flow tends to happen near market tops such as during the previous peaks in 1999 and 2007. Of course, as the CEO of Citigroup infamously once said “As long as the music is playing, you have to dance.”

There are good reasons M&A is seeing such robust activity levels. Growth is hard to come by as worldwide demand levels this year should post their lowest levels since 2009. Interest rates also remain extremely low making purchases, even very large ones possible.

In addition, companies are responding to weak organic growth potential by making acquisitions to consolidate fragmented industries, gain market share, take capacity out of the system hopefully leading to greater pricing discipline and provide economies of scale. You can see this in the semiconductor industry where over $120 billion in transactions have been announced this year. This includes Avago Technologies (NASDAQ: AVGO) buying Broadcom (NASDAQ: BCOM) for almost $40 billion earlier this year and the just announced purchase of Sandisk (NASDAQ: SNDK) by Western Digital (NYSE: WDC) last week.

I think playing the consolidation wave sweeping through various industries right now can be a profitable investment theme. Investors should stick with companies that are doing this the right way by not racking up a huge amount of debt to make purchases, that have shown they are good at integrating these acquired companies into their overall structure and that also can grow organically as well. Obviously, their stocks should also have reasonable and/or attractive valuations before being considered for an investment.

One of my favorite plays on this investment theme is United Rentals (NYSE: URI). The company, which has just a $7 billion market capitalization, is the unquestioned market leader in the very fragmented equipment rental industry. The company has more than twice the market share as its next biggest competitor yet only has 12% of the overall sales in this segment.