Infinitive conditionals with "de"
In Spanish, you already know how to express conditions using si (if). In formal contexts, such as technical manuals, safety instructions, or legal documents, there is a more concise alternative: the preposition de followed by an infinitive.
To form this conditional, replace "si + conjugated verb" with de + infinitive. The main clause remains the same, typically using the future tense, a command, or a passive construction.
| If operating the heavy machine, using the helmet will be required. | De operar la máquina pesada, se necesitará usar el casco. |
| If you lower the lever, the forklift will stop. | De bajar la palanca, el montacargas parará. |
Specifying the subject
Because the verb is in the infinitive, it isn't conjugated for a specific person or thing. When you need to explicitly state who or what is performing the action in the conditional clause, place the subject directly after the infinitive.
| If the gauge shows a problem, the alarm will sound. | De mostrar el medidor un problema, la alarma sonará. |
| If the lathe works well, you will finish the pieces. | De funcionar bien el torno, ustedes terminarán las piezas. |
Negative conditions
To express a negative condition (meaning "if not..."), simply place the word no directly between de and the infinitive.
| If the machine does not stop, this lever will be lowered for greater safety. | De no parar la máquina, se bajará esta palanca para mayor seguridad. |
| If the gear is not lubricated, the system will fail. | De no lubricar el engranaje, el sistema fallará. |
Reflexive verbs
When the conditional requires a reflexive verb, attach the reflexive pronoun to the very end of the infinitive. If you need to specify a subject, it still follows the verb and the attached pronoun.
| If the motor overheats, the alarm will sound immediately. | De sobrecalentarse el motor, la alarma sonará inmediatamente. |
| If the gear breaks, we will stop the production. | De romperse el engranaje, pararemos la producción. |