Many azo, diazo, azido, hydrazine, and azide compounds are highly flammable/explosive (with flash points below 100 degrees F). Especially dangerous is diazomethane, which is a very sensitive explosive that spontaneously explodes at 100°C, but can also explode at room temperature under high-intensity lighting or if rough surfaces are present. Methylhydrazine is also especially dangerous because of its low flash point and wide flammability limits. All compounds in this group give products that include noxious NOx. Many azides, especially the heavy metal azides, easily detonate by friction, shock, or heating. Azo dyes have been known to explode as finely divided dust dispersed in the air.

Some materials in this group can detonate. This applies in particular to organic azides that have been sensitized by the addition of metal salts or strong acids. Toxic gases are formed by mixing materials of this class with acids, aldehydes, amides, carbamates, cyanides, inorganic fluorides, halogenated organics, isocyanates, ketones, metals, nitrides, peroxides, phenols, epoxides, acyl halides, and strong oxidizing or reducing agents. Flammable gases are formed by mixing materials in this group with alkali metals. Explosive combination can occur with strong oxidizing agents, metal salts, peroxides, and sulfides.

Acutely toxic by all routes of exposure. Some of these compounds bind strongly to essential enzymes, inactivating them.

Azo compounds (RN=NR) arise from the oxidation of substituted hydrazines RHN-NHR. For example, azomethane (H3CN=NCH3) is prepared from dimethylhydrazine. The compounds are not basic in aqueous solution (because the presence of the N=N bond reduces the availability of the unshared pairs of electrons in the nitrogen atoms). They can be reduced back to the hydrazine and further to primary amines. The aforementioned hydrazines are also included in this group. They are used as moderate-strength reducing agents in organic chemistry. Diazo compounds contain the characteristic group >CN2. Thus, diazomethane has the formulas CH2N2. The organic azides are derivatives of hydrazoic acid, HN3. Alkyl azides, such as methyl azide, are prepared by treating sodium azide with the appropriate alkyl sulfate. Acyl azides have the formula RCON3. This group also covers inorganic azides, which are metal salts containing an [N3]- ion. Many inorganic azides are explosive under certain conditions, rapidly releasing N2 gas.

1,2,3-benzotriazole, azobenzene, dacarbazine, diazomethane, diphenylhydrazine, maleic hydrazine, sodium azide.