Yes. I believe this could work. Sprays are a valid alternative to smoke cleansings.
Salt water is fine. It is simple and affordable.
When I cleanse without smoke I like to use a blessing water. I simply sprinkle it around the room when I feel it is needed.
If there is a reason I need stronger cleansing, such as negative energies or spirits, I will use a full space clearing ritual. This can be done as well without smoke, though personally in my practice, I start the ritual with smoke.
As well to consider of sprays, they can be homemade and used for intentions other than cleansing and protections.
I have lemongrass spray which could be used with the intent of lust. It also as I have read, is said to be a natural insect repellent, so I have been using it as a general house spray. I can not currently indicate whether its repellent qualities have validity.
Another option is a spray with Palo Santo or sage within it.
These can be purchased, and since they are able to be purchased they clearly can be made. Though I have no personal experience making a cleansing spray with Palo Santo.
I tend to make my own with essential oil, filtered water, and rubbing alcohol. The alcohol will help the scent of a spray last if it is herbal or aroma based, as well as preserve the mix a bit. You will want to check anything homemade from time to time for freshness and safety. Throw anything with any type of growth, discoloration, or odor that is Not supposed to be present away, for the safety of yourself, others, and pets.
Do not add dry or fresh herbs or flowers into sprays. These are harder to keep preserved. I recommend, making an herbal infusion using the filtered water, you will be using in your spray. Essentially you'd be making a tea using flowers or herbs that you can use in your spray.
Otherwise essential oils work fine, and once again are easier to keep fresh.
As well, spaces can be cleansed smoke free in other ways. Stones can help. Especially protective stones such as obsidian, jet, apache tears, smoky quartz, malachite.
Keep malachite, quartz, and apache tears out of water. I wouldn't trust putting apache tears in water, I am not certain, but I personally would avoid it. Keep protective colored quartz out of direct sunlight. Try not to place these where natural sunlight will hit them. They'll fade.
Another way to cleanse without smoke can be the act of sprinkling salt. Corners are wonderful for this purpose. They tend to be a less unsightly spot for salt. The sprinkling around of plants, herbs, and flowers, can also be used for space cleansing. I love to cleanse out of door areas close to the property with fresh flower petals. These can be grown in pots. Started indoors, after the frost, and moved out of doors to finish growing. This is the less pricey way of obtaining flowers for petals and such for workings as well.
A space as well can be cleansed by sound. Chanting, prayerwork, bells, singing bowls, cymbols, rattles, drumming, or music can help a long way. Bells can be used to drive spirits away, to call helpful spirits to a place, often a spirit house, within a practitioner's space. I currently am using a bell alongside binding work.
Lastly a space can be cleansed with energy. One can visualize energy be it a mist, a light, a color, a shape etc; for the purpose of cleansing a space.
Essentially as long as you can see something within, you can add an intention to it.
An example would be I often envision a protective white light. Often I use this for my person, and family members.
It too can be used for spaces.
It matters not what you visualize but its intent.
A mist can be used for healing, cleansing, and protection.
Adding color to the visualization can give a different intention.
Red for power. Green abundance, etc.
But yes. Salt water is fine for a spray. It actually is a financially intelligent method. It is simple, and pure.
