Sectoral mutual funds are those funds which allocate entire funds into one sector. Like, Infrasructure sector fund than whole funds would be allocated in Infra. Because of nature of this fund, it considers as highest risky funds.
If sector faces tough times, so your investment also. Lack of diversification makes this fund risky. Don't allocate more than 5-10% of total portfolio.
Ideal investment period which are at least more than 7 years.