MJG Firewire Initiators, when used in Series, can fire up to a Maximum of 4 at one time. 

MJG Firewire Initiator Specs are as Follows:

Bridge Wire Resistance: 1 Ohm +/- .2 Ohm

Maximum No Fire Current: .30 Amp

Minimum All Fire Current: .60 Amp

Recommended Minimum Firing Current: .75 Amp

Recommended Nominal Firing Current:

1 Amp

Maximum Test Current: .04 Amp

MJG Firewire Initiators are intended for use with Model Rocketry and Consumer Fireworks.
Under no circumstances shall these igniters be used for anything other than their intended use. 

WARNING: If you lack adequate training in the competent handling, assembly, and firing of fireworks, do not use this material. 
Buyers and users assume all risks, responsibility and liability whatsoever from any and all injuries (including death), losses, or damages to persons or property arising from the use of these initiators purchased from Firewireinitiator.com   Under no circumstances shall firewireinitiator.com be liable for any type of damages. 
As a condition of sale, the buyer agrees to indemnify and hold harmless firewireinitiator.com and its owners/officers, from any and all claims of injury or property damage alleged to have occurred from the transportation, storage, or use of any materials purchased from firewireinitiator.com ., whether experienced by the buyer or any others the buyer has included in the distribution of said materials. The buyer agrees to abide by all federal, state, and local laws that may apply to the purchase, possession, transportation, storage, and use of these materials.